1 

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ACIllIV 

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Issued  May  28,  1908. 

U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY.— Bulletin  106. 

A.  D.  MELVIN,  Chief  of  Bureau.  '-s..^ 


)iPERIMENTS  ON  THE  DIGESTIBILITY  OF 
PRICKLY  PEAR  BY  CATTLE. 


BY 

R.  F.  HARE, 

Professor  of  Chemistry  in  the  College  of  Agriculture  and  Mechanic 
Arts  of  the  Territory  of  New  Me^aco. 


e;acc 


^  California 

Regional 

'■"acility 


WASHINGTON: 

GOVERNMENT    PRINTING   OFFICE. 

1908. 


Issued  May  28.  1908. 


U.  S.  DEPARTMENT   OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY.— Bulletin  106. 

A.  D.  MELVIN,  Chief  of  Bureau. 


EXPERIMENTS  ON  THE  DIGESTIBILITY  OF 
PRICKLY  PEAR  BY  CATTLE. 


BY 
R.  F.  HARE, 

Professor  of  Chemistry  in  the  College  of  Agriculture  and  Mechanic 
Arts  of  the  Territory  of  New  Mexico, 


WASHINGTON: 

GOVERNMENT    PRINTING   OFFICE. 
190  8. 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

IVIicrosoft  Corporation 


http://www.archive.org/details/digestpearcatOOhareiala 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Animal  Industry, 
Washington,  D.  C,  March  13,  1908. 
Sir:  I  have  the  honor  to  transmit  herewith  and  to  recommend  for 
pubhcation  as  Bulletin  106  of  this  Bureau  a  manuscript  entitled 
''Experiments  on  the  Dij^estibility  of  Prickly  Pear  by  Cattle,"  by 
R.  F.  Hare,  Professor  of  Chemistry  in  the  College  of  Agriculture  and 
Mechanic  Arts  of  the  Territory  of  New  Mexico. 

While  the  experiments  reported  in  this  paper  were  conducted  by 
Professor  Hare  in  cooperation  with  the  Bureau  of  Plant  Industry,  it 
has  been  thought  advisable  to  publish  the  paper  as  a  bulletin  of  the 
Bureau  of  Animal  Industry,  inasmuch  as  it  deals  primarily  with  the 
animal  side  of  the  subject. 

Very  respectfully,  A.  D.  Melvin, 

Chief  of  Bureau . 
Hon.  James  Wilson, 

Secretary  of  Agriculture. 

3 


LETTER  OF  SUBMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Plant  Industry, 

Washington,  I).  C,  Febniai'y  10, 1908. 

Sir:  I  have  the  honor  to  transmit  herewith  and  to  recommend  for 
publication  as  a  bulletin  of  the  Bureau  of  Animal  Industry  the  accom- 
panyinji^  manuscript  entitled  "Experiments  on  the  Digestibility  of 
Prickly  Pear  by  Cattle." 

•  This  j)aper  was  prepared  by  Prof.  II.  F.  Hare,  chemist.  College  of 
Agriculture  and  Mechanic  Arts  of  the  Territory  of  New  Mexico,  under 
cooperative  arrangements  with  this  Bureau,  and  was  submitted  for 
the  purpose  of  publication  by  Prof.  W.  J.  Spillman,  in  charge  of  Farm 
Management  Investigations. 

In  previous  bulletins  of  the  Bureau  of  Plant  Industrj^  and  the  Agri- 
cultural Experiment  Station  of  New  Mexico  much  information  has 
been  published  upon  the  practical  use  and  the  chemical  composition 
of  a  large  number  of  prickly  pears  and  other  cacti.  The  value  of  a 
feed,  however,  is  not  determined  by  the  chemical  composition  alone; 
it  is  also  necessary  to  know  the  percentage  of  digestibility  of  the  nutri- 
ents found  by  the  chemist.  This  information  is  supplied  in  the 
accompanying  manuscript. 

•     Respectfully,  B.  T.  Galloway, 

Chief  of  Bureau. 

Dr.  A.  D.  Melvin, 

Chief,  Bureau  of  Animal  Industry. 


CONTENTS. 


fage 

Introduction 7 

Method  of  conducting  digestion  experiments 7 

Definition  of  some  technical  terms  and  discussion  of  the  functions  of  foods 8 

Composition  of  feeding  stuffs 9 

Function  of  the  nutrients 11 

Method  of  determining  the  digestible  nutrients  of  prickly  pear  from  the  com- 
position and  digestion  coefficient 11 

Preparation  of  standard  rations 12 

Plan  of  the  experiments 14 

The  animals  used 14 

The  different  rations  used 15 

Description  of  the  stalls lb 

The  feeding 16 

Collecting  the  feces 17 

Collecting  the  urine 17 

Preparation  of  the  samples 18 

Report  of  the  experiments 18 

Experiment  No.  1.  Digestilulity  of  prickly  pear  (Opuntia  lindheimeri).  . .  18 

Experiment  No.  2.   Digestibility  of  prickly  pear  (Opuntia  hvris?) 21 

Experiment   No.   3.  Digestibility  of  prickly  pear  (Opuntia  cm/elmannii 

cycloides)  and  alfalfa 23 

Experiment   No.   4.  Digestibility  of  prickly   pear   (Opuntia  enye]mannii 

ryvloides )  and  cotton-seed  meal 25 

Experiment  No.  5.  Digestibility  of  a  fair  quality  of  .second-cut  alfalfa. ....  29 

Effect  of  j)rickly  j)ear  on  the  digestibility  of  other  feeding  stuffs 31 

Income  and  outgo  of  nitrogen 35 

( 'onclusions 37 


ILLUSTRATIONS. 


Ppge. 
Platk  I.  Fig.  1. — Oprintia  lindlmmeri .     Two-year-old  second  growth  of  species 
fell    in    the    first   experiment.     Kig.  2. — Opunlia   cniielmannii   nj- 
d<n(ks.     Old  plants  of  species  fed  in  the  third  experiment 8 

TKXT    KICIKK. 

Fig.  1.  The  stalls  used  in  experiments  Nos.  2  to  5 16 


EXPERIMENTS  ON  THE  DIGESTIBILITY  OF  PRICKLY 
PEAR  BY  CATTLE. 


INTRODUCTION. 

Many  chemical  analyses  have  been  made  of  a  number  cf  different 
members  of  the  cactus  family  to  determine  their  value  t^r,  a  feeding 
stuff  for  animals.*  With  this  data  we  are  enabled  to  judge  with  a 
fair  degree  of  accuracy  the  amount  of  the  varior;S  r.utrients  con- 
tained by  many  different  species  of  this  group  of  plants,  as  well  as  by 
different  parts  of  the  same  plant.  However,  as  no  record  of  diges- 
tion experiments  with  any  of  the  cacti  has  b?en  found,  it  was  impos- 
sible to  say  what  proportion  of  the  different  nutrients  were  available 
to  the  animals.  The  increased  use  of  the  prickly  pear  (the  flat- 
jointed  members  of  the  genus  Opuntia)  as  a  feed  for  all  classes  of 
ruminants,  especially  for  range  and  dairy  cattle,  makes  it  important 
for  the  proper  preparation  of  a  ration  that  the  feeder  know  how  much 
digestible  nutrients  to  expect  from  feeding  a  given  quantity  of  the 
plant  either  alone  or  mixed  with  other  feeding  stuffs.  The  following 
experiments  have  therefore  been  conducted  to  determine  the  digesti- 
bility of  prickly  pear  and  thus  guide  the  feeder  in  the  preparation  of 
rations  from  this  plant. 

The  investigations  have  been  conducted  in  cooperation  with  the 
Office  of  Farm  Management  Investigations,  Bvireau  of  Plant  Industry, 
United  States  Department  of  Agriculture.  The  author  acknowl- 
edges the  assistance  of  Dr.  David  Griffiths,  of  that  Office,  who  has 
spared  neither  time  nor  pains  in  an  effort  to  make  the  experiments 
successful.  Acknowledgment  is  made  of  the  careful  and  painstaking 
analytical  chemical  work  of  Messrs.  S.  R.  Mitchell  and  R.  B.  Deemer. 

METHOD  OF  CONDUCTING  DIGESTION  EXPERIMENTS. 

The  principle  of  conducting  a  (Hgestion  experiment  is  very  simple. 
First,  the  animal  is  fed  on  the  feeding  stuff  the  digestibility  of  which 
is  to  be  determined  until  all  other  feeds  have  been  removed  from  the 
alimentary  canal,  when  the  animal  is  said  to  be  in  a  condition  of  e(|ui- 
librium  with  this  feed.  The  animal  is  then  placed  in  a  stall  specially 
designed  for  feeding  and  for  collecting  refu.se  and  excreta  without 
waste.  It  is  then  fed  a  weighed  amount  of  the  feeding  stuff',  the  com- 
position of  which  is  determined  by  analy.sis.  All  the  refuse  is  col- 
lected, weighed,  analyzed,  and  the  amount  of  the  several  nutrients 


«See  Bulletin  60  of  the  New  Mexico  Experiment  Station. 


8  DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 

whicli  it  is  found  to  contain  is  subtracted  from  the  amount  of  the 
correspond  in  j!j  nutrients  fed.  As  nearly  a.s  possible  that  portion  of 
the  fec^s  which  corresponds  to  the  weighed  feed  eaten  is  carefully 
collected,  w(>i<rhed,  and  analyzed.  The  amoiuit  of  the  different 
nutrients  found  in  the  feces  subtracted  from  the  amount  eaten  gives 
the  amount  of  each  nutrient  digested.  This  result,  multiplied  by  100 
and  <livided  by  the  amount  eaten,  gives  the  percentage  of  digestible 
nutrients,  which  is  called  the  "coefTicient  of  digestibility." 

DEFINITION    OF    SOME    TECHNICAL   TERMS    AND    DISCUSSION    OF 
THE  FUNCTIONS  OF  FOODS. 

Most  of  the  readers  of  these  pages  will  doubtless  be  familiar  with 
the  technical  terms  that  are  used  throughout  this  bulletin  and  untler- 
stand  how  tiie  value  of  a  feeding  stuil  is  determined  from  its  analysis 
and  from  the  digestion  coefficient  of  the  several  nutrients,  but  it  may 
not  be  amiss  briefly  to  define  and  discuss  them  here  for  the  benefit 
of  the  few  who  may  not  be  thoroughly  familiar  with  them.  For  this 
reason  there  are  given  below  definitions  of  some  of  the  terms  used, 
with  the  names  of  the  constituents  that  are  usually  determined  in 
fixing  the  value  of  a  feeding  stuff,  and  a  brief  discussion  of  the  func- 
titms  of  each  in  the  animal  body. 

It  sht)uld  be  remembered  that  in  the  feeding  of  animals  the  amount 
of  nourishment  obtainetl  from  any  feetl  b}-  an  animal  does  not  alto- 
gether depend  upon  the  weight  of  the  feed  taken  into  the  body. 
Green  matter,  for  instance,  with  60  to  95  per  cent  of  water  will  not, 
of  course,  furnish  as  much  substance  as  will  cured  fodders  and  grains. 
The  scientific  feeder  must  not  only  prepare  the  rations  for  his  animals 
on  the  ])asis  of  the  amount  of  dry  matter  present,  but  it  is  also  neces- 
sary that  he  should  know  how  much  nourishment  a  given  amount  of 
this  drA'  matter  can  furnish  them.  The  dry  matter  of  the  different 
feeds  has  been  found  to  vary  greatly  in  the  amount  of  nutrients  which 
it  contains  as  well  as  in  its  digestibility.  A  feed  which  has  been 
adulterated  with  cotton-seed  hulls,  chaff,  sawdust,  or  other  fibrous 
and  insoluble  or  difficultly  soluble  matter  would  not,  for  instance, 
be  as  digestible,  and  c(msequently  could  not  furnish  as  much  nourish- 
ment pound  for  pound,  as  some  feed  in  which  the  nutrients  were  in  a 
form  more  readily  available  to  the  animal.  It  is,  therefore,  not  only 
necessary  that  the  amount  of  dry  matter  in  a  feed  be  known,  but  it  is 
equally  important  to  know^  the  character  and  composition  of  this  dry 
matter. 

The  animal  body  is  made  up  of  water,  mineral  matter  (or  ash), 
nitrogenous  matter  (or  prot^ids),  and  fat.  The  function  of  the  feed 
which  animals  eat  is  to  maintain  the  supply  of  this  material  so  that 
they  may  grow,  perform  work,  and  maintain  a  healthy  condition. 


BuL.  106,  Bureau  of  Animal  Industry,  U.  S.  Dept.  of  Agriculture. 


Plate  I. 


Fig.  1.— Opuntia  lindheimeri.    Two-Year-Old  Second  Growth  of  Species  Fed  in 
THE  First  Experiment. 


Fig.  2.— Opuntia  engelmannii  cycloides.    Old  Plants  of  Species  Fed  in  the  Third 

Experiment. 


DEFINITION    OF    TECHNICAL    TERMS.  9 

It  is  a  well-established  fact  that  all  feeds  have  certain  groups  of 
substances  that  perform  their  peculiar  functions  in  building  the  dif- 
ferent parts  of  the  animal  body,  and  the  object  of  a  chemical  analysis 
of  any  feeding  stuff  is  to  separate  and  determine  these  groups.  They 
are  usually  separated  into  the  following:  Water,  ash,  ether  extract, 
crude  fiber,  protein,  nitrogen-free  extract,  and  organic  matter.  The 
last  named  represents  a  sum  of  the  preceding  four,  and  together 
^vith  the  mineral  matter  they  are  all  called  nutrients.  The  value 
and  fimction  of  each  of  these  classes  of  nutrients  are  briefly  discussed 
below. 

COMPOSITIOX    OF    FEEDING    STUFFS. 

Water. — All  foods,  however  dry  they  may  appear,  contain  some 
moisture.  Air-dry  corn  meal  or  wheat  flour,  for  example,  which 
may  appear  perfectly  dry  will,  on  the  complete  removal  of  their 
water,  be  found  to  have  contained  from  5  to  15  per  cent.  Some  root 
crops  and  vegetables  may  contain  as  much  as  95  per  cent,  or  even 
more,  of  water.  The  water  naturally  present  in  feeding  stuffs  may 
cause  them  to  be  more  succulent  and  thus  doubtless  aids  their  diges- 
tion, but  an  increase  in  the  water  means  a  necessary  decrease  in  the 
actual  amount  of  food  material  present,  hence  its  presence  instead 
of  adding  to  merely  detracts  that  much  from  the  value  of  any  feed; 
especially  is  this  true  of  the  concentrated  feeds. 

Mineral  matter,  or  ash,  is  that  portion  which  is  left  after  complete 
combustion  of  the  plant.  While  a  certain  amount  of  ash  is  necessary 
for  supplying  mineral  matter  to  animals  and  in  building  bones  in  the 
young,  there  is  usually  an  abundance  present  in  all  foods;  and  for 
this  reason  no  commercial  value  is  placed  on  the  amount  of  ash  con- 
tained in  the  food,  as  is  the  case  with  proteids,  carbohydrates,  and 
fats. 

Protein  is  a  name  given  to  a  group  of  very  complex  compounds 
which  are  characterized  by  the  fact  that  they  all  contain  the  element 
nitrogen  combined  with  carbon,  hydrogen,  oxygen,  antl  small  amounts 
of  sulphur  and  sometimes  phosphorus.  Albumen  of  eggs,  casein  of 
milk,  and  fibrin  of  blood  are  examples  of  protein  compounds.  Pro- 
tein is  that  material  in  the  footl  which  serves  as  a  flosli  former,  and 
is  the  only  substance  of  the  food  that  can  be  used  to  buikl  nuiscular 
tissue,  skin,  hair,  horns,  blood,  and  connective  tissue.  It  may  also, 
when  in  abundance,  serve  the  function  of  the  carbohydrates  ami  fats 
of  the  food.  Alfalfa,  cotton-seed  meal,  all  the  clovers,  and  wheat 
bran  are  examples  of  feeds  rich  in  this  nutrient;  while  prickly  pear, 
straw,  roots,  and  tubers  contain  it  in  very  snuill  amounts.  Because 
of  its  importance  in  the  dietary,  and  the  fact  that  it  is  not  present 
in  sufficient  amounts  in  all  feeds  to  supply  the  needs  of  animals,  it  is 
usually  the  most  ex|)('nsiv('  of  all  the  nutrients.  In  one  State  having 
34749- Bui).  10(>-  08 2 


10  DIGEr^TIBILITY    OF    PRICKLY    PEAR    BY    CATTIE. 

a  fep(lin{j;-stu[r  law  a  valuo  of  2..i  cents  a  pouiul  was  placed  upon  the 
protein  which  the  iood  containetl,  while  the  carbohydrates  (nitrogen- 
free  extract  and  crude  fiber)  and  fats  were  priced  at  0.94  and  1.14 
cents,  respectively.  This  is  about  an  average  of  the  prices  usually 
placed  on  these  nutrients. 

In  the  Southwest,  where  alfalfa,  wheat  bran,  and  cotton-seed  meal 
are  three  of  the  i)rincipal  feeds,  animals  usually  get  an  excess  of 
protein  over  the  amount  which  they  require,  and  this  excess  is 
undoubtedly  used  to  serve  the  function  of  the  fats  and  carbohy- 
drates— that  is,  to  furnish  heat  and  other  forms  of  energy  and  to 
produce  fat.  Because  of  the  fact  that  the  feeds  mentioned  above 
are  the  most  abundant  ones  for  this  section,  if  a  commercial  value 
were  placed  on  their  various  nutrients  the  proteids  should  be  cheaper 
than  the  carbohydrates  and  fats,  and  such  is  often  the  case.  Wheat 
bran,  cotton-seetl  meal,  and  alfalfa  are  usually  found  to  be  cheaper 
than  corn  and  other  starchy  grains  and  hays. 

While  the  various  groups  of  proteid  compounds  are  alike  in  that 
the  element  nitrogen  is  common  to  them  all,  they  vary  greatly  in 
the  proportional  amount  of  nitrogen  which  they  contain  as  well  as  in 
their  value  for  building  flesh  and  muscle.  Strange  to  say,  it  is  not 
those  groups  which  contain  the  most  nitrogen  that  are  the  most 
valuable  for  this  purpose.  Those  of  most  value  as  flesh  formers  are 
the  so-called  true  proteids,  or  albumin-like  substances  that  contain 
about  16  per  cent  of  nitrogen.  These  are  most  abundant  in  grains 
and  mature  fodders.  There  are  simpler  groups  of  protein  compounds 
which  the  chemist  calls  amitls  and  amms,  or  better,  nonproteid 
nitrogen  compounds.  They  may  contain  20  per  cent  or  more  of 
nitrogen.  They  are  the  first  products  formed  by  the  plant  in  the 
synthesis  of  nitrogen  compounds  from  the  ammonia  of  the  soil. 
They  may  be  fountl  in  the  young  and  tender  parts  of  the  plant  or  in 
the  fruits,  and  in  roots  and  tubers.  It  has  been  shown  that  these 
nonproteids  can  prevent  the  waste  of  tissue  when  used  as  a  sub- 
stitute for  albumin  in  food,  but  they  are  unable  to  replace  the  latter 
in  building  flesh. 

Fat  is  the  portion  that  is  dissolved  when  the  dried  powdered  food 
is  treated  with  ether.  This  treatment  theoretically  dissolves  fats 
only,  but  practically  small  amounts  of  gums,  resins,  chlorophyll, 
and  other  substances  go  into  solution  with  this  reagent,  and  the 
material  thus  dissolved  is  often  and  perhaps  better  termed  ether 
extract.  The  fats,  like  the  carbohydrates,  are  used  as  heat  and 
energy  producers,  and  they  are  about  two  and  one-fourth  times  as 
valuable  as  the  latter  for  that  purpose.  One  pound  of  fat  yields 
4,220  calories." 


"One  calorie  is  the  aniovint  of  heat  reciuired  to  raise  the  temperature  of  1  kilogram 
of  water  1  degree  Centigrade,  or  1  pound  of  water  4  degrees  Fahrenheit. 


DETERMINING    THE    DIGESTIBLE    NUTRIENTS.  11 

Crude  jiher  is  the  portion  of  the  food  that  constitutes  the  frame- 
work of  the  plant.  In  the  analysis  it  is  the  part  remaining  after  the 
finely  ground  food  has  been  thoroughly  treated  successively  with 
ether  and  hot  dilute  acid  and  alkali. 

Nitrogen-free  extract  is  represented  by  the  sugars  and  starches,  and 
includes  all  of  those  compounds  of  carbon,  hydrogen,  and  oxygen 
that  are  dissolved  by  boiling  the  fat-free  material  consecutively  for 
thirty  minutes  each  in  dilute  acid  and  alkali  of  definite  strengths. 
All  of  this  group  of  bodies,  together  with  that  part  of  the  crude  fiber 
which  is  digested  by  the  animal,  are  collective!}^  called  carbohydrates. 
They  serve  the  same  function  as  the  fats  in  the  animal  system,  but 
are  not  so  concentrated  a  food.  One  pound  of  carbohydrates  3'ields 
about  1,860  calories,  hence  we  say  that  fats  which  yield  4,220  calories 
per  pound  have  two  and  one-fourth  times  the  value  of  carbohydrates 
as  heat  producers. 

FUNCTION    OF   THE    NUTRIENTS. 

The  two  main  functions  of  food  are  to  produce  tissue  and  to  fur- 
nish energy.  Proteids  alone  are  used  for  the  former  purpose,  while 
fats,  carbohydrates,  and  excess  of  proteids  can  all  be  used  for  the 
latter.  The  amount  of  food  used  for  building  tissue  is  comparatively 
small,  hence  the  ratio  of  proteid  to  nonproteid  nutrients  may  be 
quite  wide,  especially  for  grown  animals  that  are  doing  hard  work. 

Since  the  important  fimctions  of  any  food  are  performetl  by  the 
proteids  and  nitrogen-free  nutrients  (fats  and  carbohydrates)  they 
contain,  the  amount  of  these  present  and  in  a  form  available  to  the 
animal  is  a  measure  of  the  value  of  that  food. 

METHOD  OF  DETERMINING  THE  DIGESTIBLE  NUTRIENTS  OF 
PRICKLY  PEAR  FROM  THE  COMPOSITION  AND  DIGESTION 
COEFFICIENT. 

An  average  of  several  analyses  of  a  certain  variety  of  prickly 
pear  {Opujitia  lindheimeri)  shows  it  to  liave  the  following  composi- 
tion: Water,  83.41  per  cent;  ash,  3.48  per  cent;  protein,  0.75  per 
cent;  ether  extract,  0.31  per  cent;  crude  fiber,  2.64  percent;  nitrogen- 
free  extract,  9.41  per  cent;  total  organic  matter,  13.11  per  cent. 

By  feeding  this  plant  to  steers  we  find  the  following  coeflicient 
of  digestion  of  the  nutrients  present  for  tliis  class  of  animals:  Pro- 
tein, 58.25  per  cent;  fat  (etlier  extract),  67.90  per  cent:  crude  liber, 
41.32  per  cent;  nitrogen-free  extract,  82.59  per  cent.  With  these 
figures  we  calculate  the  following  digestible  nutrients  from  the  above 
analyses  by  multiplying  each  nutrient  by  its  coeflicient:  Proteids, 
0.45;  fat,  0.21;  carbohydrates,  7.77.  The  nutritive  ratio,  or  the 
ratio  between  digestible  proteids  and  nitrogen-free  material,  i.  e.,- 
fat  X  2.25  -\-  total  carbohydrates,  in  this  sample  of  the  plant,  is  1 
to  18.3. 


12 


DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 


PREPARATION  OF  STANDARD  RATIONS. 

As  before  staled,  the  value  oi  a  feed  does  not  necessarily  depend 
upon  the  amount  of  proteids,  carbohydrates,  and  fats  which  it  con- 
tains, but  rather  upon  the  amount  of  these  containetl  in  the  feed 
that  is  available  to  animals.  If  digestion  experiments  show  that 
a  comparatively  large  amount  of  the  nutrients  pass  into  the  feces, 
then  in  order  that  the  animal  may  secure  sufficient  nutrients  to 
supply  the  purpose  sought  there  must  be  a  corresponding  increase 
of  the  ration.  For  the  guiilance  of  the  feeder  in  the  proper  prepa- 
ration of  his  ration,  the  tligestion  coefficient  has  been  determined 
for  practically  all  ordinary  feeds  anil  for  the  several  kinds  of  farm 
animals.  Experience  has  proven  that  the  best  results  are  obtained 
in  feeding  when  the  digestible  nutrients  are  fed  to  the  animal  in 
certain  definite  amounts.  Tables  of  feeding  standartls  have  been 
compileil  by  German  and  American  scientists  in  which  are  given  the 
daily  amounts  of  each  nutrient  required  by  our  common  farm  animals 
of  a  given  weight  and  for  a  specific  purpose.  In  the  feeding  of  milch 
cows,  for  example,  the  standard  fixeil  by  the  German  scientist  Wolff 
is  the  one  probably  most  used  in  this  country  at  present.  It  is 
based  on  ol)servation  of  the  feeding  practices  of  the  best  German 
feeders,  together  with  feeding  experiments  by  trained  specialists. 
There  is  a  prevalent  opinion  in  the  I'nited  States  that  the  Wolff 
stan<lard  for  milch  cows  is  somewhat  higher  in  proteids  than  is 
necessary  for  the  best  American  ration.  Several  attempts  have 
been  made  by  scientists  in  the  United  States  to  determine  what  the 
proper  standard  is  for  this  country.  Below  is  given  a  tal)le  taken 
from  the  Connecticut  (Storrs)  Experiment  Station  rept)rt  for  1894,  in 
which  is  given  the  German  standard,  together  with  four  rations 
which  have  been  proposed  by  different  authorities  for  the  United 
States. 


Table  1. — (Unnan  (Wolff's)  standard  ration.  togctJicr  with  averages  of  some  American 
rations  and  a  tentatively  suggested  ration  per  1,000  pounds  live  iveight. 


Wolff's  (( iermaii  i  sluiulani 

Average  of  128  -Viucrifuii  ratiou:-..  coin- 
piled  by  the  Wisconsin  E.\porinient 
Station 

Average  of  lt>  rations  as  fed  In  Connecti- 
cut in  1892-93 

Average  of  2a  rations  as  fed  in  Connecti- 
cut in  l«)2-'.>4 

Tentatively  suggested  ration  « 


Organic 
matter. 

Digestible  nutrients 

Protein. 

*Fat. 

Carbo- 
hydrates. 

Fuel 
value. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

Calories. 

24.0 

2.50 

0.40 

12.50 

29,000 

24.5 

2.15 

.74 

13.27 

31,250 

26.4 

2.48 

.94 

14.09 

34.800  ■ 

2«.8 

2.51 

.90 

13.92 

34,350 

2.'j.0 

2.50 

.5  to  .8 

13  to  12 

31,000  : 

1 

Nutri- 
tive ratio. 


1:6.9 
1:6.5 


1:6.3 
1:5.6 


n  In  thi."*  suggested  ration  the  fuel  value  could  be  supplied  by  about  0.5  pound  of  digestible  fat  and  13 
pounds  of  digestible  carbohydrates;  by  0.6  pound  of  digestible  fat  and  12.5  pounds  oT  digestible  carbo- 
hydrates; or  oy  0.8  pound  of  digestible  fat  and  12  pounds  of  digestible  carbohydrates. 


PREPARATION    OF    STANDARD    RATIONS.  13 

It  will  be  seen  from  the  table  that  about  the  only  material  change 
recommended  by  American  scientists  consists  in  an  increase  of  the 
fats  and  carbohydrates.  It  would  appear  that  this  much  difference 
might  almost  result  from  individuality,  and  the  feeder  would  be  safe 
in  using  any  of  these  rations  that  common  sense,  good  judgment,  and 
his  experience  with  the  individual  animals  would  indicate  to  him  to 
be  best.  In  New  Mexico,  where  proteid  feeds  are  cheap,  the  nutri- 
tive ratio  of  the  Wolff  standard  would  probably  not  be  too  narrow. 
In  fact,  narrower  rations  than  those  proposed  by  him  are  used  here 
constantly  with  splendid  results. 

By  the  use  of  the  above  table  a  balanced  ration  can  be  prepared 
from  prickly  pear  when  its  digestible  nutrients  are  known,  by  so 
mixing  it  with  other  feeds  as  to  obtain  the  nutrients  in  the  right  pro- 
portion. Suppose,  for  example,  we  desire  to  prepare  a  ration  com- 
posed in  part  of  prickly  pear  for  a  1,000-pound  milch  cow  yielding 
22  pounds  of  milk  per  day.  Using  the  Wolff  standard  of  2.5  pounds 
protein,  0.5  pound  fats,  and  13  pounds  carbohydrates  as  our  basis, 
and  feeding  100  pounds  of  prickly  pear  per  day,  the  cow  would  get 
the  following  nutrients,  as  calculated  above  from  the  species  Opuntia 
lindlieimeri:  Proteids,  0.45  pound;  fats,  0.21  pound;  carbohydrates, 
7.77  pounds.  This  leaves  a  balance  of  2.05  pounds  protein,  0.29 
pound  fat,  and  5.23  pounds  carbohydrates  to  be  supplied  by  some 
other  feed.  Since  the  ratio  of  proteids  to  nonproteids  (nutritive 
ratio)  in  this  variety  of  pear  is  1  to  21.7',  and  a  ratio  of  1  to  5.7  is 
the  Wolff  standard  for  such  a  cow,  it  is  evident  that  some  feed  rich 
in  protein  should  be  mixed  with  the  prickly  pear  to  narrow  it  down 
to  this  ratio.  Cotton-seed  meal,  wheat  bran,  or  alfalfa  could  be  used 
for  this  purpose,  but  cotton-seed  meal,  if  fed  in  quantity,  contains 
so  much  protein  that  it  makes,  perhaps,  too  narrow  a  ration  for  the 
best  results;  besides,  animals  scour  when  fed  cotton-seed  meal  and 
prickly  pear  alone,  and  if  possible  these  should  be  fed  in  connection 
with  some  cured  fodder. 

In  Bulletin  60  of  the  New  Mexico  Experiment  Static^n  a  balanced 
ration  of  jirickly  pear  is  di.scussed  and  rations  containing  this  feed 
are  suggested.  At  the  time  the  bulletin  was  written  the  coeHicient 
of  digestion  for  prickly  pear  had  not  been  determined,  and  in  calcu- 
lating the  rations  its  digestibility  was  a.ssumed  to  be  the  same  as  that 
of  green  corn  fodder."  That  the  digestion  coedicient  of  prickly  pear, 
calculated  from  the  coeHicient  of  green  com  fodder,  is  very  similar  to 
that  obtained  from  actual  digestion  ex|)eriments  may  be  seen  from 
the  table  following. 

« Set' Bull  Hi  n  77,  Offiic  uf  Kxpcriinciil  Stalinns,  liiiicd  Slalis  Dciiartiin'nl  of 
Agricultun',  p.  82. 


14 


DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 


Tabi.k.  2.-~Tolal  niitrifnts  of  prickly  pear  yOpxintia  lindhcimeri ) .  the  digestibh  niitri- 
mis  (US  ohiainid  by  e.i prrinirnt.  and  the  rahulatcd  digestible  7iutriinls  obtained  by  using 
the  digestion  coejficient  of  green  corn  fodder. 


Niinie  tif  nutrient. 


Prickly  pear: 

Composition 

Digestilile  nutrients  as  determined 

l>igestit>le  nutrients  as  calculat«d  irom-  data 
ol>t«ine<l  wit i>  preen  com  f(Kider. .        


Protein. 

Fat. 

Nitrogen- 
free 
extract. 

Filjer. 

rarl)o- 
hydrates. 

Percent. 

Per  cent. 

Per  cent. 

Percent. 

Percent. 

0.75 

0.31 

9.41 

2.61 

2.01 

.« 

.21 

7. 77 

1.09 

8.86 

.49 

.22 

(•..S7 

1.76 

R.63 

From  tlie  forojjoin*;  table  it  may  he  seen  that  the  coefficients  of 
(liijestion  of  green  corn  fodder  that  were  used  for  calculating  the 
digestibility  of  prickly  pear  in  the  preparation  of  a  balanced  ration 
in  Bulletin  60  are  sufficiently  close  to  allow  the  ration  there  given  to 
remain  unchanged. 

The  proteids  of  the  prickly  pear  do  not  appear  to  be  quite  as 
digestible  as  those  of  green  corn  fodder,  the  fats  are  about  the 
same  in  both,  while  the  nitrogen-free  extract  is  more  for  the  prickly 
pear,  the  crude  fiber  is  less,  but  the  total  digestible  nutrients  are 
about  the  same,  being  slightly  in  favor  of  prickly  pear. 

PLAN  OF  THE  EXPERIMENTS. 
THE    ANIMALS    USED. 

Five  different  digestion  experiments  are  included  in  this  study^. 
In  all  cases  wild  range  steers  from  2  to  3  years  olil  were  the  animals 
selected.  The  steers  being  very  wild  were  quite  difficult  to  handle 
properly,  but  it  seemed  impossible  to  get  tame  steers  and  at  the  same 
time  those  accustomed  to  eating  prickly  pear.  In  fact,  a  gentle 
steer  is  practically  unknown  on  the  ranges.  Plenty  of  milch  cows 
were  available,  but  were  not  used  because  of  the  difficulty  of  keeping 
i^eparate  the  liquid  and  solid  excreta.  Both  sheep  and  goats  eat 
j>rickly  pear,  ])ut  none  that  could  be  used  in  this  work  were  found 
convenient;  besides,  steers  were  preferred,  it  being  deemed  more 
desirable  to  get  the  data  for  cattle,  since  they  are  fed  this  plant 
more  extensively  than  are  any  other  animals.  J*]xperience  has  shown 
that  there  may  be  a  slight  difference  between  the  digestion  coeffi- 
cient obtained  from  sheep,  goats,  and  cattle,  yet  for  all  practical 
purposes  this  factor  may  be  assumed  to  be  the  same  for  all  ruminants. 
Two  steers  were  used  in  each  of  the  experiments  so  as  to  minimize 
any  difference  due  to  individual  animals  or  slight  errors  due  to 
manipulation.  It  is  usually  customary  to  use  two  animals  in  this 
work:  sometimes  more  are  used,  and  of  course  the  larger  the  number 
the  more  trustworthv  should  be  the  result. 


PLAIS'    OF    THE    EXPERIMENTS.  15 

THE    DIFFERENT    RATIONS    USED. 

The  first  experiment  was  conducted  at  San  Antonio,  Tex.,  in 
January,  1906.  In  this  experiment  the  steers  were  fed  prickly  pear 
alone  for  about  three  weeks.  During  the  last  four  days  they  were 
confined  in  stalls  and  all  their  feed  and  refuse  were  carefulh'  weighed, 
the  feces  and  urine  being  collected  in  a  manner  described  later. 

Experiments  Nos.  2,  3,  4,  and  5  were  all  conducted  in  the  spring 
of  1907  at  the  Agricultural  College  of  New  Mexico.  Grade  Hereford 
steers  were  used  in  each  experiment. 

In  experiment  No.  2  prickly  pear  was  fed  alone,  as  in  experiment 
No.  1  conducted  at  San  Antonio  the  previous  year. 

In  experiments  Nos.  3  and  4  prickly  pear  was  mixed  with  other 
feeding  stuffs  (alfalfa  in  experiment  No.  3,  cotton-seed  meal  in  No. 
4),  to  determine  what  effect,  if  any,  these  feeds  might  have  on  the 
digestibility  of  the  prickly  pear,  or  vice  versa. 

In  experiment  No.  5  the  digestibility  of  the  alfalfa,  which  was  fed 
with  prickly  pear  in  experiment  No.  3,  was  determined. 

The  digestibility  of  the  cotton-seed  meal  when  fed  alone  was  not 
determined  as  was  done  with  alfalfa,  it  being  decided  to  accept  the 
digestion  coefficients  secured  by  other  experiments  for  this  feed. 

Summarized,  the  experiments  were  made  to  determine — 

(1)  Digestibility  of  prickly  pear  (Opuntia  lindheimeri). 

(2)  Digestibility  of  prickly  pear  {0.  Isems?). 

(3)  Digestibility  of  prickly  pear  {0.  engelmannii  cycloules)  and 
alfalfa. 

(4)  Digestibility  of  prickly  pear  {0.  engelmanmi  cydoiibs)  and 
cotton-seed  meal. 

(5)  Digestibility  of  a  fair  cjuality  of  second-cut  alfalfa. 

DESCRIPTION    OF   THE    STALLS. 

A  good  idea  of  the  stalls  lused  in  these  experiments  may  be  obtained 
from  figure  1.  They  were  made  of  proper  length  and  lifreadth  so  that 
the  steers  could  lie  down  comfortably,  but  not  wide  enough  to  permit 
them  to  turn  around.  The  stalls  used  at  the  college  were  about  8 J 
feet  long  and  4  feet  wide.  Most  of  the  floor,  which  had  a  slight  inclina- 
tion from  both  front  and  rear  toA^ard  the  center  and  to  one  side  of  tlie 
stall,  was  covered  with  thick  rubber  cloth.  Tlie  inclination  of  tlie 
floor  allowed  all  the  urine  to  nni  to  the  middle  of  the  stall,  where  it 
was  caught  in  a  galvanized  iron  trough  and  conducted  to  vessels  out- 
side the  stall,  as  shown  in  the  illustration.  The  urine  trougli  ran  the 
entire  width  of  the  stall  near  the  center  and  just  beneath  the  floor. 
A  narrow  1-inch  strip  was  nailed  across  the  floor  of  the  stall  in  such  a 
manner  as  to  prevent  any  H(juid  feces  from  running  into  the  urine 


16 


DIGESTIBILITY    OF    PRICKLY    PKAR    BY    CATTLE. 


trou«;li.  The  side  and  back  walls  of  the  stalls  were  lined  with  gal- 
vanized iron  wherever  there  was  any  danger  from  s})attering  of  feces. 
The  feed  trough  was  made  ])erfectly  tight,  and  so  placed  that  the 
animals  could  eat  with  comfort  and  not  waste  their  feed.  The  stalls 
were  covered  and  placed  in  a  position  to  make  the  animals  as  com- 
fortable as  possible. 


Fig.  1.— The  stalls  used  in  experiments  Nos.  2  to  5. 


THE    FEEDING. 

The  preliminary  feeding  period  which  preceded  the  experiment 
proper  was  never  less  than  seven  days,  usually  more.  In  this  time 
there  was  little  possibility  of  any  other  food  being  left  undigested  in 
the  animals'  systems.  The  steers  were  then  placed  in  the  stalls  and  a 
weighed  amount  of  the  feed  was  given  them  twice  each  day,  a  sample 
being  reserved  for  analysis  each  time  before  weighing.  The  prickly 
pear  was  first  prepared  by  singeing  the  spines  by  means  of  a  brush 
fire  and  chopping  the  singed  stems  into  small  pieces  with  a  large  knife 
or  root  chopper.  A  quantity  of  this  feed  was  kept  before  the  animals 
most  of  the  time  for  a  period  of  five  days,  the  refuse  being  removed 
and  weighed  twice  each  day. 


METHOD    OF    COLLECTING    THE    EXCRETA.  17 

COLLECTING    THE    FECES. 

After  the  preliminary  period  of  a  .week  or  more  the  steers,  wliich 
during  this  time  had  the  run  of  a  small  inclosure,  were  placed  in  their 
stalls,  but  the  feces  were  not  collected  for  twenty-four  hours  afterwards. 
This  was  assumed  to  be  the  feces  from  the  first  feed  that  was  weighed 
to  them  the  day  before.  While  this  is  an  unsatisfactory  method  of 
determining  the  first  weighed  feed,  it  seemed  the  best  that  could  be 
done,  and  it  is  believed  that  the  error  resulting,  if  any,  was  not  large 
when  the  sum  of  the  feces  for  the  five  days  was  taken.  It  is  a  difficult 
matter  to  mark  the  beginning  of  a  digestion  experiment  with  steers. 
In  experiments  of  this  kind  with  man  or  animals  other  than  ruminants 
it  is  customary  to  use  charcoal  or  some  indigestible  material  of  a  dif- 
ferent color  from  the  feces,  which  will  give  a  distinct  line  of  separation 
between  feces  from  weighed  and  unweighed  food,  but  with  the  steers 
the  marking  of  the  weighed  feed  was  not  so  simple.  The  experi- 
ment was  tried  of  giving  a  small  handful  of  weighed  uncnished  corn 
as  recommended  in  Minnesota  Experiment  Station  Bulletin  99,  but 
the  method  was  found  unsatisfactory  in  this  instance  because  at  times 
the  corn  did  not  appear  for  three  or  four  days,  and  then  it  did  not  all 
come  together. 

Usually  in  digestion  experiments  with  animals  it  is  customary  to 
fasten  rubber  bags  to  them  by  means  of  a  harness  to  catch  the  excreta, 
but  this  was  wholly  impracticable  with  any  range  steers  that  could  be 
obtained.  Hence  it  was  necessary  to  arrange  the  stalls  as  well  as 
we  could  for  the  separation  of  feces  and  urine,  and  to  keep  an  attend- 
ant constantly  with  the  steers  during  the  entire  experiment.  The 
work  was  made  unusually  difficult  because  the  steers  were  wild  and 
somewhat  nervous  all  the  time.  Then,  too,  as  the  prickh'  pear 
caused  diarrhea  or  '' scouring"  in  the  animals,  extra  care  had  to  be 
exercised  to  prevent  loss  of  feces  from  spattering  and  otherwise;  but 
it  is  believed  that  with  the  precautions  taken  the  method  used  was 
quite  as  satisfactory  as  the  method  of  collecting  in  bags. 

COLLECTLNG    THE    URINE. 

Since  the  digestibility  of  a  footl  is  shown  by  the  difference  between 
the  amount  eaten  and  the  amount  undigested,  all  of  which  is  found 
in  the  feces,  there  can  be  no  object  in  collecting  the  urine  when  the 
digestibility  of  the  food  is  all  that  is  sought.  This  is  therefore 
collected  only  when  it  is  desired  to  know  something  of  the  metab- 
olism of  the  nitrogen  of  the  food.  The  solid  matter  of  urine  other 
than  the  inorganic  salts  is  principally  urea  and  other  highly  nitroge- 
nous compounds  resulting  from  a  waste  of  nmscular  and  otiier  nitrog- 
enous tissue,  the  kidneys  ])eing  the  principal  organs  through  which 

34749— Bull.  10«>— 08 3 


18  DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 

this  waste  is  excreted  fn^n  the  l)0(ly.  Tlie  excess  of  nitrogenous 
matter  from  the  digested  proteids  of  the  food  may  also  be  found  in 
tlie  urine. 

In  tlie  experiments  the  urine  was  collected,  weighed,  and  analyzed 
for  the  purpose  of  studying  the  income  and  outgo  of  nitrogen  with 
the  different  feeds,  in  some  of  which  the  proteids  were  present  in 
very  small  amounts,  while  in  others  the  nutritive  ratio  was  much 
narrower  than  that  given  by  Wolff  for  oxen  at  rest  in  stalls.  The 
results  of  this  study  of  nitrogen  metabolism  are  given  in  Table  17, 
and  are  discussed  under  ''Income  and  outgo  of  nitrogen"  in  another 
part  of  this  bulletin. 

PKEPARATIOX    OF    THE    SAMPLES. 

Samj)les  of  the  feed  and  refuse  were  collectetl  twice  daily,  and  of 
feces  and  urine  once  each  day.  After  a  moisture  determination 
had  been  made  on  the  samples  of  feed  and  refuse  for  each  day  the 
dry  matter  from  them  all  was  mixed  for  one  composite  sample. 

The  dail}'  samples  of  feces  and  urine  were  analyzed  separately 
in  all  experiments  except  for  the  urine  in  experiment  No.  1.  In 
this  instance  one  composite  sample  was  made  of  all  daily  samples. 

In  collecting  the  samples  of  feed,  refuse,  and  feces  about  200 
grams  of  the  fresh  material  were  taken  in  a  large  porcelain  dish  and 
j)laced  in  the  hot  New  Mexico  sun  where  it  soon  reached  an  air-tlry 
condition.  The  drj^  material  was  then  pulverized  ami  was  reatly 
for  the  analyses,  which  were  made  according  to  the  methods  of  the 
Association  of  Official  Agricultural  Chemists. 

REPORT  OF  THE  EXPERIMENTS. 
Experiment  No.  1. — Digestibility  of  Prickly  Pear  (Opuntia  Hndheimeri). 

This  experiment  was  conducted  at  the  ranch  of  Mr.  Alexander  Sin- 
clair, near  San  Antonio,  Tex.  This  locality  was  selected  because  in 
that  section  the  prickly  pear  grows  much  more  luxuriantly  than  it 
does  in  the  vicinity  of  the  New  Mexico  Agricultural  College,  and  cat- 
tle there  are  more  accustomed  to  eating  the  plant  than  are  the  cattle 
of  New  Mexico;  in  fact,  the  steers  that  were  fed  at  the  college  had  to 
be  trained  to  eat  prickly  pear,  and  in  consequence  ate  not  more  than 
half  the  amount  eaten  by  the  Texas  steers.  Moreover,  during  part 
of  the  time,  at  least,  what  they  did  eat  was  little  relished,  except 
when  fed  in  connection  with  some  other  feed. 

In  this  experiment  two  3-year-old  range  steers,  weighing  about  800 
pounds  each,  were  used.  They  were  fed  for  a  preliminary  period  of 
ten  days  before  being  placed  in  the  stalls.  The  experiment  began  at 
noon  January  2,  1906,  and  continued  until  noon  of  Januarv  6.     The 


DIGESTIBILITY    OF    PRICKLY    PEAR    ALONE. 


19 


steers  were  placed  in  a  barn  with  plenty  of  light  and  air,  and  were 
well  protected  from  the  cold.  They  remained  in  good  condition  dur- 
ing the  entire  experiment,  except  that  they  scoured  quite  badly,  as 
animals  always  do  on  an  exclusive  prickly  pear  diet.  The  fact  that 
these  animals  scoured  is  not  surprising  when  one  considers  that  in 
eating  100  pounds  of  prickly  pear,  the  average  daily  ration  during  the 
five  days,  they  consumed  2.95  pounds  of  inorganic  matter  or  ash, 
which  doubtless  means  more  than  twice  this  amount  of  salts  more  or 
less  purgative  in  their  character.  The  steers  also  obtained  86.4 
pounds  (or  over  10  gallons)  of  wat^r  from  100  pounds  of  prickly  pear, 
and  this  would  doubtless  aid  the  salts  in  their  purgative  action.  The 
water  obtained  from  the  feed  was  more  than  was  drunk  by  the  steers 
in  experiment  No.  5  where  alfalfa  alone  was  fed  and  in  which  an 
average  of  only  48  pounds  a  day  was  drunk.  The  steers  in  experi- 
ment Xo.  1  took  no  water  during  the  experiment  except  that  obtained 
from  the  feed. 

In  Table  3  is  given  the  composition  of  the  composite  sample  made 
up  of  daily  samples  of  the  pear  fed  and  refused  during  the  four  days 
the  animals  were  in  the  stalls.  There  are  also  given  analyses  of  daily 
samples  of  the  feces  from  both  steers.  From  the'se  figures  with  the 
weights  of  the  dr\^  matter  in  feed  and  feces  have  been  calculated  the 
data  given  in  Table  4. 


Table  3. — Experiment  Xo.  1 — Composition  of  the  prirkhj  pier  faL  of  th'  r»fnse.  and 

of  the  feces. 

[Nutrients  reported  water  free.] 


Water. 


Prickly  pear,  as  fed 

Prickly  pear,  water  free. 
Refuse  water  free — 

Steer  Xo.  1 

Steer  No.  2 

Feces  steer  Xo.  1— 

First  day 

Second  day 

Third  day 

Fourth  day 

Feces  .steer  No.  2— 

First  day 

Second  day 

Third  day 

Fourth  day 


Per  cent.  Per  cent 


S6.38 


Ash. 


2.95 
21. 69 


21.69 
21.69 


85.76 

.36.91 

85.59 

42.64 

88.63 

42.79 

86.65 

42.34 

82.83 

45.93 

81.39 

45.33 

8S.89 

.36. 74 

87.62 

35.32 

Protein.a      Fat." 


Per  cent.  Per 
0.72 
5.27 


5.27 

6.28 
6.28 
7.79 
5.97 

5.85 
6.40 
7.79 
5.58 


cent. 
0.19 
1  42 

1.42 
1.42 

1.51 
1..30 
1.57 
1.27 

1.24 
1.31 
1.36 
1.18 


Cru<le 
fll'^r. 


Per  cent. 

1.77 

1.3.00 

13.00 
13.00 

22.94 
21. 73 
19. 38 
21.01) 

21.  46 
20.91 
19.  82 


^'Y^"i  Organic 
eximct.     '"'*"<^'- 


Per  cent. 

8.02 

58.62 

58.62 
58.62 

32. 36 
28. 05 
28.  47 
29. 36 

25.52 
26.  ai 
34. 29 
34.  45 


Per  cent. 
10.70 
78.31 

78.31 
78.31 

6;i.09 
.=>7. 36 
57.21 
57.66 

54. 07 
.54.67 
t«.  26 
64.68 


"The  words  •' protein"  and  "  (at"  are  used  here  and   elsewhep' in  this  hulli-tin  to  denote,  respecr 
lively,  crude  protein  and  ether  extract. 


20 


DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 


T.\BLE  4.- 


Weight  of  the  feed,  refuse,  anri  frees  in  experiment  No.  1,  uith  thf  calculated 
digest ioi}  coefficients. 


STEER  NO.  1. 


Dry 
matter. 


Orama. 

Total  prickly  pear  fed 25,542.  7 

Total  prickly  pear  refused 441.3 


Total  prickly  pear  eaten.  25,101. 4 


Feces: 

First  day ;  1,913.3 

Second  day ,  1,546.2 

Third  day 2,063.7 

Fourth  day |  2,730. 1 


Total  feces  droppe<l 8,253. 3 

Digested 'l6,84S.  1 

Coefficient    of   digestion    (per  j 
cent) 67.12 


Ash.     I  Protein. 


Fai. 


Oramt. 

5,540.0 

95.7 


Orams. 

1,346.1 

2a  3 


Oramt. 

382.7 

6.3 


5,444.3       1,322.8 


356.4 


706.2 

659.3 

883.1 

1,155.9 


iaa2 

97.1 
160.8 
163.0 


3,404.5 
2,039.8. 

37.46 


541.1 
781.7 


59.03 


289 
20.1 
32.4 
34.7 


116.1 
240.3 


Crude    r^'^""-  Organic 
^^'-      extXt.    ""^tter. 


Oramt.      Oramt.      Orams. 

3,320.6     j  14,973.  3       20,002.7 

57.4    !      258.6  345.6 


3,263.2     14,714.7       19,657.1 


438.9 
336.0 
399.9 
575.0 


619. 1 

I  433.7 
I  587.5 
i      801.5 


1,207.1 

886.9 

1,180.6 

1,574.2 


1,749.8    j  2,441.8 
l,5ia4    [12,272.9 


4,848.8 
14,808.3 


41.31 


83.40 


STEER  No.  2. 


Total  prickly  pear  fed 

Total  prickly  pear  refused 

24,422. 6 

889.4 

5,297. 3 
192.9 

1,287.1 
46.9 

346.8 
12.6 

3,174.9 
115.6 

14,316.5 
521.6 

19,125.3 
696.7 

Total  prickly  pear  eaten. 

23,5312 

5,104.4 

1,240.2 

334.2 

3,059. 3 

13,794.9 

18,428.6 

Feces: 

First  day 

Second  dav 

1,697.6 
2,390.5 
1,749.8 
2,489.5 

8,327.4 
15,205.8 

64.61 

65.86 

779.7 

1,083.6 

642.9 

879.3 

99.3 
153.0 
136.3 
l.'8.9 

21.1 
31.3 
2.^8 
29.4 

364.3 
493.9 
346.8 
584.3 

433.2 
622.7 
600.0 
85i.6 

917.9 
l,:i06.9 

Third  dav       

] ,  106. 9 

Fourth  day 

1,610.2 

Total  feces  dropped 

Digested 

3,385.5 
1,718.9 

33.67 

35.57 

527.5 
712.7 

57.47 

5S.25 

105.6 
228.6 

68.38 

67.90 

1,795.3 
1,264.0 

41.32 

41.32 

2,5ia5 
11,281.4 

81.78 

82.59 

4,191.9 
14.236.7 

Coefficient    of   digestion    (per 
cent  1          

77.03 

Average  per  cent  digested  by 
two  steers «> 

74.12 

Note.— 453.4  grams  equal  1  jMjund. 

0 

The  figures  given  above  speak  fairh*  well  for  the  digestibility  of 
the  prickly  pear.  The  coefficient  for  dry  matter  is  equal  to  an 
average  of  that  obtained  from  our  best  feeds 

This  experiment  shows  that  the  digestion  coefficient  for  the  ash 
of  prickly  pear  is  low,  but  this  was  to  be  expected  because  of  the 
large  amount  of  ash  always  present  in  these  plants.  Animals  assim- 
ilate more  ash  from  prickly  j)ear  with  the  low  digestion  coefficient 
of  this  nutrient  than  they  obtain  from  other  feeds.  For  example, 
the  ash  assimilated  from  100  pounds  of  prickly  pear  by  steer  No.  1 
of  this  experiment  amounts  to  1.11  pounds;  while  steer  No.  1  in 
experiment  No.  5,  where  alfalfa  alone  was  fed,  assimilated  only  0.6.3 
pound  from  15  pounds  of  alfalfa. 


DIGESTIBILITY    OF    PRICKLY    PEAR    ALONE.  21 

The  digestibility  of  the  other  nutrients  is  found  to  compare  very 
favorably  with  other  standard  feeds,  the  coefficient  for  nitrogen-free 
extract  being  unusually  high. 

Experiment  No.  2. — Digestibility  of  Prickly  Pear  {Opuntia  Isevisf). 

This  experiment  and  the  three  following  were  all  conducted  with 
the  same  two  steers.  They  were  grade  Herefords  that  had  been 
grain  fed  and  were  ready  for  the  market  at  the  time  the  experiment 
was  begun.  This  fact  rendered  them  less  satisfactory  for  feeding 
on  prickly  pear  alone;  and  to  make  the  matter  worse  the  feeding 
was  done  in  the  spring,  when  many  of  the  joints  were  young  and 
least  palatable  to  animals.  In  view  of  this  fact  the  daily  ration, 
amounting  to  only  53.52  pounds  for  steer  No.  1,  and  72.18  pounds 
for  steer  No.  2,  was  considerably  short  of  enough  for  maintenance. 
The  animals  lost  flesh  rapidly  on  this  ration,  but  unfortunately  we 
can  not  say  just  how  much,  since  they  were  not  weighed  after  the 
experiment.  However,  by  reference  to  Table  17,  it  may  be  seen 
that  the  excreted  nitrogen  during  the  five  days  was  in  excess  of  the 
nitrogen  of  the  feed  by  46.9  grams  for  steer  No.  1  and  63.2  grams 
for  steer  No.  2,  making  a  daih^  loss  of  58.6  grams  of  proteids  for 
steer  No.  1  and  of  79  grams  for  steer  No.  2. 

By  referring  to  Table  5  it  will  be  seen  that  both  steers  received 
much  less  than  a  maintenance  ration.  Steer  No.  1  ate  only  6.64 
pounds  of  dry  matter,  when  for  maintenance  he  should  have  had 
15.1  pounds.  Steer  No.  2  ate  9.36  pounds  out  of  16.7  pounds  required, 
and  the  nutritive  ratio  of  the  dry  matter  was  1  to  33  for  both  steers. 

The  results  of  this  experiment  agree  fairly  well  with  those  obtained 
at  San  Antonio  in  experiment  No.  1,  the  greatest  difference  being 
in  the  amount  of  protein  and  fiber  digested.  The  increased  amount 
of  fiber  digested  in  this  experiment  might  be  explained  by  the  fact 
that  the  plants  were  mostly  young  and  succulent  joints  in  which  the 
fiber  had  not  developed  to  such  an  extent  from  the  more  digestible 
hydrated  cellulose.  Steer  No.  1  obtained  46.3  pounds  of  water  from 
the  prickly  pear  eaten.  He  drank  in  addition  an  average  of  7.6 
pounds  daily.  Steer  No.  2  obtained  62.4  pounds  of  water  from  his 
feed  and  drank  in  addition  5.4  pounds. 

Table  5. — Experiment  Xo.  2 — Composition  of  the  prickly  pear  fed.  of  the  rcjiise.  and  of 

the  feres. 

[Nutrients  reported  water  free.] 


Water. 


I  Per  cent. 

I'nckly  pear  fed 86.  45 

Prickly  poar,  wiitor  fro" 

Refuse,  waU'r  free— Ste<'r  No.  1. 
Steer  No.  2. 


Ash. 

Protein. 

Per  cent. 

Per  cent. 

2.85 

0.57 

21.05 

4.22  ' 

21.82 

4.64 

Crude     N't^"-   Organio 


Fat.      I    V^^r  free 

extract 


Per  cent.  Per  cent.  Per  cent.   Per  cent. 

0.23  2.25'          7.6.";             10.70 

1.71  16.81           56.41             78.95 

1.46  17.14           54.94'          7S.  18 


22 


DIGESTIBILITY    OF    PRICKLY    PEAK    BY    CATTLE. 


Table  5. — Experiment  No.  2 — Composition  of  the  prickly  pear  fed,  of  the  refuse,  and  of 

the  feces — Continued. 


Water.  \     Ash. 


Feccsof  steor  No.  1:  Percent.   Percent. 

Flrstday 76.72!  .3S.85 

Second  day j  75.40|  44.49 

Thirdday 73. .36  I  .38.62 

Fourthday 74.55  31.74 

Fifthday I  72.04  31.42 

FtH^s  of  stwr  No.  2:  I 

Firstday I  82.50  37.07 

Secondday I  81.04  41.75 

Thirdday |  80.01  40.01 

Fourth  day 84  46  31..32 

Fifthday 76.69  i  .36.86 


Protein. 


Percent. 
6.98 
6.87 
7.42 
a49 
6.81 

7.28 
5.78 
5.91 
5.91 
6.91 


Fat. 


Percent. 
1.33 
1.28 
1.51 
1.77 
1.95 

1.49 
1.16 
1.40 
1.54 
1.98 


Crude    !^"'Vi^£*""  Organic 


Percent.^ 
1&94  j 
19.22 
21.64 
20.07 
24.52 

21.38 
21.07 
19.82 
19.56 
24.57 


Per  cent. 
33.90 
28.14 
30.81 
37.93 
35.30 

32.78 
30.24 
.32.86 
41.67 
29.68 


Percent. 
01.15 
55.51 
61.. 38 
68.26 
68.58 

62.ft3 
58.25 

68.68 
6.3.14 


Table  6. 


-Weight  of  the  feed,  refuse,  and  feces  in  experiment  No.  2,  vnth  the  calculated 

digestion  coefficient. 


STEER  NO.  1. 


Dry 
matter. 


Ash. 


Total  prickly  pear  fed 

Total  prickly  pear  refused . 


Grams.  Orams. 
18,749.3  3,946.7 
'  3,694.5    I      806.1 


Protein. 


Orams. 
791.2 
171.4 


Total  prickly  pear  eaten. 


Feces: 

First  day... 
Second  day. 
Third  day.. 
Fourth  day. 
Fifth  day... 


Total  feces  dropped 

Total  digested 

Coefficient   of  digestion    (per 
cent) 


15,054.8    ,  3,140.6 


619.8 


912.6 

1,287.8 

G00.0 

917.5 

1,382.1 


354.5 
572.9 
206.5 
291.2 
434.3 


63.7 
88.5 
51.2 
77.9 
94.1 


5.190.0       1,919.4 


375.4 


p.,       i    Crude    |N"/«»«"i  Organic 


Grams.      Orams.      Orams. 
320.6       3,114.3     10,576.5 
53.9  633.2    |  2,029.9. 


266.7 


12.0 
16.5 
10.4 
16.2 
27.0 


82.2 


9,684.8       1,221.2    i      244.4 


65.52 


38.88 


39.43 


Grams. 
14,802.6 
2,888.4 


2.481.1 


172.8 
247.5 
149.3 
184.1 
339.0 


8,546.6 


309.5 
362.4 
212.6 
348.1 
487.7 


11,914.2 


558.1 
714.9 
423.5 
626.3 
947.8 


1,092.7       1,720.3         3.270.6 


1,388.4       6,826.3         8.643.6 


55.96 


79.87 


72.55 


STEER  NO.  2. 


Total  prickly  pear  fe<l '23, 753. 8 

Total  prickly  pear  refused 2, 530. 0 


Total  prickly  pear  eaten.  21 ,  223. 8 


Feces: 

First  day 1,554.5 

Secondday 1,784.1 


Third  day 

Fourth  day 

Fifth  day 

Total  feces  dropped 

Total  prickly  poar  digested 

Coefficient   of   digestion    (per 

cent) 

Average  coefficient  of  digestion . 


1,228.0 
1,434.3 
1,981.4 


7,982.3 


13,241.5 


62.40 
63.96 


5,000.2 
552.0 


1,002.4 
117.4 


406.2 
36.9 


4, 448.  2 


885.0 


360.3 


576.3 
744.9 
491.3 
449.2 
730.3 


113.2 
103.1 
72.6 
84.8 
136.9 


2,992.0 


510.6 


1,456.2 


32.74 
X>.81 


374.4 


42.31 
40.87 


23.2 
20.7 
17.2 
22.1 
39.2 


122.4 


3,945.5     13,399.5 
433.6       1,390.0 


18, 753.  6 
1,978.0 


3,511.9     12.009.5    ;  16,675.6 


332.3 
375.9 
243.4 
280.5 

48&8 


509.5 
539.5 
403.5 
597.7 
588.2 


978.2 

1,039.2 

736.7 

985.1 

1,251.1 


1,718.9    I  2.638.4 


68.86 
09.02 


1,792.0       9,371.1 


51.02 
53.99 


4,990.3 


78.03 
78.  a5 


11,785.3 

70.12 
71.39 


DIGESTIBILITY    OF   PRICKLY    PEAR    AND    ALFALFA.  23 

Experiment  No.  3. — Digestibility  of  Prickly  Pear  (Opuntiaengelmanniicycloides) 

AND  Alfalfa. 

Since  prickl}'  pear  will  not  furnish  a  balanced  ration  when  fed 
alone,  but  requires  some  feed  of  a  relatively  high  protein  content 
as  a  supplement,  the  effect  of  alfalfa  on  the  digestibility  of  the  prickly 
pear  has  here  been  tried.  Steer  No.  1  was  given  an  average  of  4.5 
pounds  of  alfalfa  daily,  while  4.72  pounds  was  given  to  steer  No.  2. 
In  addition  they  were  given  all  the  prickly  pear  they  would  eat, 
which  was  42.16  pounds  for  steer  No.  1,  and  57.18  pounds  for  steer 
No.  2.  The  prickl}"  pear  used  was  Opuntia  engelmannii  cycloides, 
which  is  a  larger  stemmed  plant  than  most  of  the  native  prickly 
pears,  and  the  animals  seemed  to  relish  it  better  than  they  did 
O.  laevisf,  the  variety  used  in  the  preceding  experiment. 

The  results  obtained  in  feeding  this  ration  to  steer  No.  1  were 
for  some  unaccountable  reason  very  unsatisfactory.  The  dry  mat- 
ter digested  amounted  to-  only  56.81  per  cent  and  the  ash  to  16.87 
per  cent,  while  the  protein  coefficient  was  minus  16.54  per  cent. 
This  negative  value  for  protein  means  that  the  protein  of  the  feces 
amounted  to  more  than  that  of  the  feed,  which,  of  course,  is  an 
error.  Whether  this  was  due  to  blood  or  cleavage  products  in  the 
feces,  we  can  not  say.  The  percentage  of  nitrogen  in  the  feces 
was  unusualh"  high,  but  duplicate  analyses  of  these  were  made  that 
checked  within  reasonable  limits  of  working  error.  Only  29,92 
per  cent  of  the  fiber  was  digested  by  this  animal,  but  the  amounts  of 
fat,  nitrogen-free  extract,  and  organic  matter  seemed  to  compare 
favorably  with  the  coefficients  of  these  nutrients  from  the  feed  of 
steer  No.  2.  Assuming  the  digestibility  of  prickly  pear  fed  in  this 
experiment  to  be  an  average  of  the  coefficients  for  the  two  varieties 
determined  in  experiments  Nos.  1  and  2,  we  have  by  the  use  of  this 
factor  calculated  the  digestion  coefficient  of  the  alfalfa  that  consti- 
tuted the  other  .portion  'of  the  ration.  The  coefficients  obtained 
for  alfalfa  with  steer  No.  1  are  quite  as  unsatisfactory  as  were  those 
obtained  from  this  steer  for  prickly  pear.  They  were  all  far  below 
the  normal  digestion  coefficients  for  this  feeding  stuff,  the  results 
for  ash  being  minus  38.9  per  cent.  While  the  results  obtained  from 
steer  No.  1  with  this  ration  are  all  recorded  in  the  following  tables, 
it  is  very  evident  that  the  coefficients  found  can  not  ])e  used  in  tlie 
calculation  of  rations  of  either  prickly  pear  or  alfalfa.  We  liave 
therefore  omitted  them  from  all  averages. 

With  steer  No.  2  the  results  show  an  increase  in  the  digestibility 
of  the  nutrients  of  both  feeds,  and  this  is  just  wiiat  inigiit  i)e  ex]K'cted 
with  this  ration. 

For  a  comparison  of  the  digestion  coefficients  of  prickly  pear  and 
alfalfa  obtained  in  the  following  table  with  those  of  prickly  pear 
obtained  in  the  other  experiments  and  of  alfalfa  obtained  both  here 
ami  at  the  other  experiment  stations,  see  Table  14. 


24 


DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 


Table  7. — Experiment  No.  3 — Composition  of  the  prickly  pear  and  alfalfa  fed,  of  the 

refuse,  and  of  the  feces. 

[Nutrients  reported  water  tree.] 


Water. 


Asb.       Protein. 


Prickly  f)e»ir  water  free 

Alfalfa  water  free 

Kefuse  of  priclcly  i>ear,  steers 

Nos.  1  and  2 

Kefuse  of  alfalfa,  steers  Nos.  1 

and  2 

Feces  of  steer  No.  1 : 

First  day 

Second,  day 

Third  day 

Fourth  day 

Fifth  day 

Feces  of  steer  No.  2: 

First  day 

Second  day 

Third  day 

Fourth  day 

Fifth  day 


i  I 

Per  ceni.  Per  cent.  Per  cent. 


None. 
None. 


18.75 
10.09 


18.75 


2.98 
14.09 


2.98 


None. 

73.56 
82.79 
80.89 
80.10 
79.02 

82.00 
83.67 
80.88 
83.13 
83.46 


None.        None. 


35.62 
27.87 
•29.46 
26.85 
25.80 

29.65 
27.40 
28.71 
23.84 
28.10 


7.60 
9.80 
9.42 
9.01 
9.10 

7.40 
8.20 
8.24 
7.13 
7.09 


Fat. 


Crude 
fiber. 


Nitrogen- 
free  ex 
i    tract. 


Per  cent.  Per  cent. 
1.48  I  12.22 
2.07  32.28 


1.48 

None. 

2.02 
1.93 
2.18 
1.87 
1.50 

1.91 
1.80 
1.82 
1.76 
1.64 


None. 

25.79 
32.68 
20.62 
28.00 
29.65 

36.80 
27.71 
26.00 
29.18 
31.83 


Per  cent. 
64.57 
41.47 

64.57 

None. 

28.97 
27.72 
38.32 
34.27 
33.95 

24.04 
34.89 
35.23 
38.09 
31.34 


Organic 
matter. 


Per  cent. 
81.25 
89.91 


None. 

04.38 
72.13 
70.54 
73.15 
74. 20 

70.35 
72.60 
71.29 
76.16 
71.90 


Tabi.k  S. — Weight  of  the  feed,  refuse,  and  feces  in  experiment  No.  3,  tvith  calculated 

digestion  coejjicients  of  both  feeds  used  and  of  each  separately. 

STEER  NO.  1. 


Dry 
matter. 


.\sh. 


Crude    ,^f!-;  Organic 


tract. 


Qrams.  |   Orams. 

Total  prickly  pear  fid 33, 994. 7       6, 374. 0 

Total  prickly  pear  refused 14.236.6    I  2.669.  4 


Grams.      Grams. 

1,012.0  503.1 

424. 3  210. 7 


Grams.  Grams.  \  Grami. 
4.1.54.1  21.950.4  \  27,620.7 
1.739.7       9,192.6    !  11,567.2 


Totivl  prickly  pear  eaten .  19, 758. 1       3, 704. 6 


ToUl  alfalfa  fed 19,685.6    I      977.3 

Total  alfalfa  refused None,  i      None. 

Total  alfalfa  eaten. . 


Feces: 

First  day... 
Second  day. 
Third  day.. 
Fourth  day. 
Fifth  day... 


9,685.6    I      977.3 


2. 164. 9 
2,  .502. 2 
2,062.0 
2.980.0 
3.008.5 


771.1 
722.4 
607.5 
800.1 
776.2 


587.7    I      292.4       2,414.4     12,757.8 


1,.?64.7 
None. 


200.5       3,126.5       4,016.6 
None.        None.  '      None. 


1.364.7 


200.5 


164.5 
254.0 
194.2 
268.5 
273.8 


43.7 

5o;o 

45.0 
55.7 
45.1 


Total  feces  dropped 

Coefficient  of  digestion  of 
prickly  j»ear  and  alfalfa  (per 
c-cnt) 

Total  alfalfa  undigested 

Total  feces  from  prickly  pear. . 

Total  prickly  pear  digested 

Coefficient  of  digestion  of 
prickly  pear  (p<>rcent) 

Coefficient  of  digestion  of  al- 
falfa (percent)  " 


12,807.6  3,077.3 

56. 84  21.  46 

4,27.3.3  .597.6 

8,534.3  3,079.7 

11,223.8  -624.9 

56.81  -16.87 

39.35  !        .38.90 


1,155.0 


239.5 


40. 84  I        51.  41 

470. 1     '  163.  4 

694.9  76.1 

-97.2  216.3 

-16.54  }        73.97 

I 

29.76  26.54 


3,126.5       4.016.6 


558.3 

627.3 

847.1 

718.7 

425.2 

790.1 

834.4 

1,021.2 

892.0 

1,021.4 

3.5.57.0  4,178.8 

35.80  i        75.09 

1,865.0  1,211.4 

1,692.0  2,967.4 

722.4  9,790.4 

29.92  [        76.74 

26.65  ,        57.04 


15,053.5 


8, 708. 3 
None. 


8, 708. 3 


1,.393.8 
1,869.8 
1, 454.  5 
2, 179. 9 
2,232.3 


9, 130. 3 

61.57 
3,675.8 
5,454.5 
9,599.0 

63.09 

42.24 


a  Calculated  on  the  assumption  that  the  coefficient  of  digestion  of  the  prickly  pear  used  in  this  experi- 
ment was  an  average  of  the  two  varieties  fed  in  experiments  Nos.  1  and  2. 


PRICKLY    PEAR    AND    COTTON-SEED    MEAL. 


25 


Table  8. — Weight  of  the  feed,  refuse,  and  feces  in  experiment  Xo.  3,  uifh  calculated 
digestion  coefficients  of  both  feeds  used  and  of  each  separately — Continued. 

STEER  NO.  2. 


Dry 
matter. 


Ash. 


Grains.      Grams. 

Total  prickly  pear  fed 39,146.1       7,339.9 

Total  prickly  pear  refused 12. 033. 3       2. 256.  2 


Total  prickly  pear  eaten .  27, 112.  8       5.  OSS. ; 


Total  alfalfa  fed 10, 157. 3       1, 024. 9 

Total  alfalfa  refused None.        None. 


Grams. 

1, 166. 6 

358.6 


Grams. 
579.4 
178.1 


Crude    -N'tn^fr  Organic 


Grams.  Grams.  Grams. 
4,783.7  25,276.4  31,806.2 
1.470.5    '  7,769.9         9,777.1 


80S.0 


401.3       3.313.2    ,17,506.5 


1,431.2 
None. 


210.2    I  3,278.8 
None.        None. 


Total  alfalfa  eaten . 


10.1.57.3-       1,024.9       1,431.2 


Feces: 

Fi rst  day 1 ,  948. 5 

Second  day 2,604.6 

Third  day .'.    2.820. 2 

Fourth  day 3,188.4 

Fi  fth  day I  2. 160. 1 


577.  7 
713.7 
809.7 
760.1 
607.0 


Total  feces  dropped 1 12, 721. 8 

Coefficient     of     digestion     of 

prickly  pear  and  alf.ilfa  (per 

cent) 65.87 

Total  alfalfa  undigested 4,  481. 3 

Total  feces  from  prickly  pear. .  8,240.  5 
Total  prickly  pear  digested ....  18, 872. 3 
CoeflScient     of     digestion     of 

prickly  pear  (percent) 09.61 

Coefficient  of  digestion  of  al-  j 

falfa  (per  cent) '        68.  41 


3,468.2 


43.22 
626.7 
2,841.5 
2,242.2 

44.11 


144.2 
213.6 
232.4 
227.3 
153.2 


970.7 


56.65 
493.0 
477.7 
189.3 


60.65 


4,212.2 
None. 


22. 029. 1 

9, 132.  4 
None. 


3,278.8       4,212.2     ,     9,1.32.4 


37.2 
46.9 
51.3 
56.1 
35.4 


717.0 
721.7 
733.3 
930.4 
687.6 


226.9     1  3,790.0 


472.4 
908.7 
993.5 
1,214.5 
676.9 


1,370.7 
1,890.9 
2,010.5 
2,428.3 
1.553.1 


4. -266.0         9,253.5 


62.89           42.51  S0.o6  70.34 

147.2  1,95.5.8  1,270.4  3,854.8 

79.7  1,834.2  2.995.6  5.398.7 

321.6  1,479.0  14,510.9  16,630.4 


80.14  44.  «t 

52. 28  37. 29 


82. 88  75.  49 

78.65  64.38 


ExpERiME.NT  No.  4. — DIGESTIBILITY  OF  Prickly  Pe.\r  {Opuntia  engelmannH cycloides) 

.\NU  Cotton-seed  Me.\l. 

In  the  prickly-pear  region  of  Texas  a  ration  consisting  of  this  feed- 
ing stuff  with  cotton-seed  meal  is  very  common.  It  is  customary  and 
better  to  give  the  cattle  either  the  run  of  a  dry  grass  pasture  or  some 
coarse  feed  in  connection  with  this  ration,  as  it  will  serve  the  double 
purpose  of  widening  the  too  narrow  ration  produced  from  too  much 
cotton-seed  meal  and  tend  to  check  the  scouring  which  results  from 
the  use  of  the.se  two  feeds  alone.  Bulletin  74  of  the  Bureau  of  Plant 
Industry,  United  States  Department  of  Agriculture,  gives  a  num- 
ber of  rations  as  used  by  Texas  stockmen  and  dairymen  made  uj)  of 
prickly  pear  and  cotton-seed  meal  in  varying  amounts  that  were 
usually  fed  together  with  other  feeds.  However,  in  the  ration  u.sed 
in  this  digestion  experiment  prickly  pear  and  cotton-.seed  meal  alone 
were  u.sed,  becau.se  it  was  desired  not  only  to  determine  the  coellicient 
of  digestion  of  the  ration  of  the  two  when  fed  together  but  also  to 
use  the  weights  obtained  for  a  calculation  of  the  coefficient  of  diges- 
tion of  cotton-seed  meal,  and  these  would  have  been  complicated  by 
the  addition  of  other  feeds  to  the  ration. 


26  DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CAITLE. 

SU'or  No.  1  ate  an  averaj^o  of  4.78  pounds  of  cotton-seed  meal  and 
37.28  pounds  of  prickly  pear  daily.  This  made  only  14.14  pounds  of 
dry  matter,  which  was  about  1  pound  short  of  a  maintenance  ration 
of  dry  matter;  but  the  proteids  were  in  excess  of  the  amount  re(juired 
for  maintenance  by  more  than  a  pound,  and  while  the  carbohydrates 
were  a  trifle  short  the  excess  of  both  proteids  and  fat  made  the  total 
nutrients  more  than  the  amount  required  for  maintenance.  The 
nutritive  ratio  of  the  feed  for  this  steer  was  1  to  4.49,  and  he  gained 
1,551.9  grams  of  proteids  in  the  five  days. 

Steer  No.  2  ate  a  daily  average  of  4.99  poimds  of  cotton-seed  meal 
and  47.04  pounds  of  prickly  pear.  This  gave  him  17.35  pounds,  or 
nearh'  1  pound  more  than  a  maintenance  ration,  of  dry  matter 
which  contained  a  slight  excess  of  all  the  nutrients.  The  nutritive 
ratio  of  his  feed  was  1  to  5.52.  He  gained  for  the  five  days  1 ,262.5 
grams  of  protein. 

The  digestion  coefficient  for  the  two  steers  agreed  very  closely, 
but  while  the  coefficient  for  the  protein  of  cotton-seed  meal  and  of 
cotton-seed  meal  with  prickly  pear  was  about  what  might  be  expected, 
the  coefficient  for  the  protein  in  the  prickly  pear  was  a  minus  quan- 
tity to  about  the  same  degree  for  both  steers.  This  error  might  be 
attributed  to  several  causes.  It  rftay  have  been  because  the  composite 
sample  of  pear  used  for  analysis  did  not  contain  sufficient  proteids 
to  be  representative  of  the  prickly  pear  fed.  It  had  only  2.59  per 
cent  of  protein,  while  an  average  of  the  five  samples  of  this  species 
recorded  in  Bulletin  60  of  the  New  Mexico  Experiment  Station  had 
3.99  per  cent,  and  an  average  of  all  prickly  pears  contained  4.47 
per  cent  protein  in  the  air-dry  material.  It  is  barely  possible  also 
that  some  error  may  have  been  introduced  here  by  hairs  from  the 
shedding  animal  getting  into  the  feces.  It  is  also  possible  that  it 
resulted  from  a  larger  amount  of  metabolic  products  formed  from  a 
feed  like  cotton-seed  meal  with  its  high  protein  content.  Steer 
No.  1,  for  example,  got  hardly  1  pound  of  protein  from  the  prickly 
pear  during  the  five  days,  but  obtained  nearly  10.5  pounds  from 
the  cotton-seed  meal;  and  the  large  amount  of  protein  from  the 
latter  source  may  have  increased  the  metabolic  nitrogen  in  the  feces 
and  thus  made  it  appear  that  the  feces  from  the  prickly  pear  con- 
tained more  protein  than  did  the. feed,  when  in  reality  it  may  have 
been  due  in  part  at  least  to  cleavage  products  resulting  from  the 
protein  of  the  cotton-seed  meal  fed. 

As  a  further  attempt  to  explain  these  negative  results  Professor 
Spillman  has  suggested  the  very  probable  theory  that  it  resulted 
from  the  reduced  digestibility  of  the  protein  of  the  cotton-seed  meal, 
due  to  the  laxative  action  of  the  prickly  pear  forcing  the  other  feed 
from  the  digestive  tract  before  its  protein,  which  digests  slowly, 
had  been  thoroughly  acted  upon,  but  not  before  the  easily  digested 


COMPOSITION    OF    PRICKLY    PEAR    AND    COTTON -SEED    MEAL.     27 

carbohydrates  had  been  more  completely  assimilated.  Since  cotton- 
seed meal  is  a  substance  rich  in  protein  and  the  prickly  pear  is  very 
poor  in  this  ingredient,  a  very  slight  reduction  of  the  digestion  coef- 
ficient of  the  former  would  and  did  result  in  an  apparent  negative 
result  for  the  latter. 

The  average  of  three  digestion  coefficients  for  cotton-seed  meal 
as  given  in  Bulletin  77  of  the  Office  of  Experiment  Stations,  United 
States  Department  of  Agriculture,  was  used  in  calculating  these 
coefficients.  Since  the  cotton-seed  meal  used  in  this  experiment  was 
adulterated  with  hulls,  as  may  be  seen  from  the  crude-fiber  analysis, 
it  may  be  that  the  figures  from  the  above  bulletin  did  not  represent 
the  coefficients  for  the  meal  used  in  the  experiment.  If,  however, 
we  assume  the  digestibility  of  prickly  pear  fed  to  be  the  same  as  that 
obtained  in  previous  experiments,  and  calculate  the  coefficients  of 
digestion  for  the  nutrients  of  cotton-seed  meal  accordingly,  we  find 
them  somewhat  similar  to  those  given  in  Bulletin  77.  It  is  inter- 
esting to  note  that  both  of  our  calculations  show  over  100  per  cent 
of  the  fat  digested,  which  agrees  with  some  of  the  results  recorded 
in  the  above  bulletin,  and  substantiates  also  the  statement  made 
by  Jordan  in  his  work  on  "The  Feeding  of  Animals"  that  "pure 
vegetable  fats  and  oils  are  quite  completely  emulsified  and  absorbed" 
bv  animals.  . 


Table  No.  9. — Experiment  No.  4 — Composition  of  the  prickly  pear  and  cotton-seed 
meal  fed,  of  the  refuse,  and  of  the  feces. 

[Nutrients  reported  water  free.] 


Prickly  pear,  water  free 

Cotton-seed  meal 

Refuse  of  prickly  pear,  steer 

No.l 

Refuse  of  prickly  jjear.  steer 

No.  2 

Refuse    of   cotton-seed    meal, 

steers  Nos.  1  a  nd  2 

Feces  of  steer  No.  1 : 

First  day 

Second  day , 

Third  day 

Fourth  day , 

Fifth  day 

Feces  of  steer  No.  2: 

First  day 

Second  day 

Third  day 

Fourth  day 

Fifth  day 


Water. 


Per  cent. 

72.97 

5.09 


77.53 
82.51 
82.08 
82.63 

79.58 

81.  C8 
81.94 
84.  13 
82.75 
8.V  15 


Ash. 


Per  cent. 

21.74 

6.68 

21.89 

24.87 

a6s 

.iO.  45 
30.85 
31.76 
34.82 
35.09 

26.21 
.•«).69 
31.78 

;«;.  10 

34.70 


Protein. 


Per  cent. 
2.59 
44.25 

2.85 

2.85 

44.25 

13.09 
12.85 
12.92 
12.14 
11.38 

14.76 
13.38 
14.22 
9.95 
9.86 


Per  cent. 
2.03 
10.02 

1.25 

1.51 

10.02 

1.28 
1.55 
1.18 
1.13 
1.03 

1.71 
1.29 
.97 
1.05 
l.Of. 


Crude 
nber. 


Per  cent. 
11.44 
11.02 

12. 26 

11.38 

11.02 


Nitrogen' 
free  ex- 
tract. 


20.14 
19.83 

21.62 
19.93 
16.93 
22.04 
19.  45 


Per  cent. 
62.20 
28.03 

61.75 

59.39 

28.03 


19.13  36.05 

la  00  3<"..  75 

18.12  36.02 


31.77 
32.07 

35.70 
34.71 
.36.10 
30.86 
.34. 93 


Organic 
matter. 


Per  cent. 

78.26 
93.32 

78.11 

75.13 

93. 32 

69.55 
69.15 
68.24 
65.18 
(i4.91 

7.3. 79 
69. 31 

68.22 

(a.90 

»«.  .30 


28 


DIOESTIBILTTY    OF    PRICKLY    PEAR    BY    CATTLE. 


Tahi.i:   N(».  I(».      Wiitjhl  of  iht/icii.  n futit ,  avd/urs  in  crjiirinient  No.  -i .  vith  calculaUd 
(li(j(sliun  cutjlicunts  of  both  ficds  uM'd  and  of  each  separately. 


STEEK  NO.  1. 


Dry 
matter. 


Oramg. 

Total  prickly  pear  ted |29,722. 2 

Total  prickly  pear  refused 7,904.5 


Ash. 


Orams. 
0,461.0 
1.743.4 


Protein. 


Orama. 
7C9.8 
227.0 


Total  prickly  iiear  eaten. |21, 7.57.  7       4.7IS.2  542.8 

Total  eotton-.seed  meal  fetl |I0,758.0     i      718.0    j  4,760.4 

Total  cotton-seed  meal  rpfused.        409.8  31.4     I      207.9 


Total   cotton-seed    meal  , 
eaten 10,288.2 


087.2     I  4,552.5 


Feces—  First  day 1  2,033. 5 

.Second  day.., 2,430.8 

Third  day '  1.SC3.7 

Fourth  day 1,544.2 

Fifth  dav I  2,5.50.5 


019.2 
751.8 
591.9 
5.37. 7 
89.-..  0 


260.2 
313.1 
24a  8 
187.5 
290.2 


Fat. 


Grams. 

G03.4 

99.0 


crude    l^l^f- 
tract. 


filter. 


Oramt.      Grams. 

3,400.2      18,487.2 

97a  4     !  4,91&1 


503.8       2,423.8      13,560.1 


1,078.0 
47.1 


1,185.5 
,51.8 


3,015.5 
13M 


1,030.9 


26.0 
37.8 
22.0 
17.4 
2a  3 


1,1,1X33     2,883.9 


389.0 
4.38.0 
3:i7.7 
311.0 
5a5.8 


733.1 
895.5 
071.3 
490.0 
833.2 


Total  feces  dropped |10.428.7       3,.W5.0 


Coefficient  of  digestion  of  prick- 
ly pear  and  cotton-seed  meal 
(percent) 

Total  cotton-seed  me^l  undi- 
gested   

Total  feces  from  prickly  pear". . 

Total  prickly  pear  digested. . . . 

Coefficient  of  digestion  of  prick- 
ly i»ear  (per  cent) 

Coefficient  of  digestion  of  cot- 
ton-seed meal  (percent)''  . .. 


07. 46 


1,297.8 


129.5     I  1,982:  1        ;j,023.  7 


91.50 


2,7a5.8 

.524. 3 

.528.1 

09.1 

504.3 

7  722.9 

2,871.3 

709.7     1 

60.4 

1,477.8 

14.(m.8 

1.84a  9 

-22a  90  ' 

443.4 

94a  8 

04.50 

:«t.oi 

-41. S 

'88.08 

.39.03 

72.84 

47.42 

77. 51 

102  7 

.37. 04 

77.97 


1,1.3a  3 
2,487.4 


Oiiganic 
matter. 


Orams. 
23, 260. 6 
6,221.1 


17,039.5 


10,039.4 
4.38.4 

9,601.0 


1,414.3 
1,685.0 
1,271.8 
1,006.5 
1,65.5.5 


7,03.3.  1 


73.60 

2,294.0 
4,7:58.5 
12,301.0 


81. 67  '  72. 19 

I 

64.83  '  75.09 


STEER  NO.  2. 


Total  prickly  f>ear  fed 3.5,  S78. 3 

Total  prickly  pear  refused 7,279. 1 


7,799.9 
l,8ia3 


929.2 
207.5 


728.3       4,104.5 
109. 9    '      828.  4 


Total  prickly  1*11  r  eaten.  2.S,'i99.  2 

Total  cotton-seed  me.al  led 10, 758. 0 

Total  cotton-aeed  meal  refused .         20. 9 


5,988.6 


721.7 


618.4     I  3,27a  1 


718.6    I  4,700.4 
1.4!  9. 2 


1,078.0 
2.1 


1,185.5 
2.3 


10,737.1 


Total  cotton-seed    meal 
eaten 

Feces— First  day 1, 296. 1 

Second  day 2, 975. 4 

Third  day 2,487.0 

Fourth  day '  3,073. 1 

Fifth  day !  2,090.1 

Total  feces  dropp<>d 

Coefficient  of  digestion  of  prick- 
ly pear  and  cotton-seed  meal 
(percent) 


717.2 


4,751.2     ,  1,075.9     !  1,183.2 


22,.3ia4 
4, 323. 0 


17,993.4 


3,015.0 
5.9 


3.009. 


.3.39. 7 

913.2 

790.6 

1,109.4 

,  933. 5 


191.3 
398.1 
.35.3.7 
305.8 
2a5  2 


22.2 
38.4 
24.1 
;{2.3 
28. 5 


280.2 
59.3.0 
421.2 
677.3 
523.2 


462.7 
l,a32.7 
898.0 
94a  3 
9.39.7 


I2,.522.3     I  4,08a  4     |   1,514.1 


2,494.9       4,281.4 


68.17 


.39.05 


72. ;« 


28,078.4 
5, 468. 8 


10,039.5 
19.5 


10,020.0 


950.4 
2,0«i2.2 
1,097.0 
1,963.7 
1,7.50.0 


8, 4.35. 9 


a  Calculated  on  the  jissumptlon  that  the  digestibility  of  t 
the  two  fed  in  experiments  Nos.  1  and  2. 

*>  Coefficient  of  digestion  for  cotton-seed  meal  used  in  these 
Office  of  E.xperiment  Stations.  I'nited  States  Department  of 


91.41  44.05  I        77.97  i  74.15 

his  variety  of  cactus  was  the  average  of 


calculations  was  taken  from  Bulletin  77, 
.Vgriculture. 


DIGESTIBILITY    OF    SECOND-CUT    ALFALFA. 


29 


Taf.le  No.  10. —  Weight  of  the  feed ,  refuse,  and  feces  in  experiment  No.  4,  with  calculated 
digestion  coefficients  of  both  feeds  used  and  of  each  separately — Continued. 

STEER  NO.  2-Continued. 


Average  coefficient  of  digestion 
of  prickly  pear  and  cotton- 
seed ineal 

Total  cotton-seed  meal  undi- 
gested   

Total  feces  from  prickly  peam. 

Total  prickly  pear  digested 

Coefficient  of  digestion  of  prick- 
ly pear  (per  cent) 

Average  coefficient  of  digestion 
of  prickly  pear  (per  cent) 

Coefficient  of  digestion  of  cot- 
ton-seed meal  (percent)*  . .. 


Dry 
matter. 


(i7.  82 


Grams. 


.•«».04 


2, 823. 9  ,  547.  2 
9,698.4  I  3,539.2 
18,900.8     I  2,449.4 


eti.OS 


40.<I0 


'     Crude     Nitrogen-'  Organic 
Protein.  I      Fat.  Crude  ,  Organic 


Grams.      Grams.      Grams.      Grams.  I   Grams. 


551.1 
9«3.0 
-241.3 


72.1  j  526.5  j  1,185.8  2,394.8 
73.4  I  1,968.4  ,  3,095.6  6,041.1 
545.0    I  1,307.7     .14,897.8       16,568.5 


-34.82  88.13 

-38.31   j         88.11 
69.  89  104.  6 


39.92  J        82.79  73.28 

39.48  82.23  72.74 

34.06  ;        72.71  77.28 


"Calculated  on  the  assumption  that  the  digestibility  of  this  variety  of  cactus  was  the  average  of 
the  two  fed  in  experiments  Nos.  1  and  2. 

ftCoefflcient  of  digestion  for  cotton-seed  meal  used  in  thoso  calculations  was  taken  from  Bulletin  77, 
Office  of  Experiment  Stations,  United  States  Department  of  Agriculture. 

Experiment  No.  5. — Digestibility  of  a  Pair  Quality  of  Second-Cut  Alfalfa. 

This  experiment  was  made  to  determine  the  chgestion  coefficients 
of  the  alfalfa  that  was  used  in  experiment  No.  3.  The  results  are 
given  in  Table  12,  from  which  it  will  be  seen  that  the  coefficients 
obtained  in  this  experiment  are  about  the  same  as  those  determined 
by  other  experiment  stations.  For  some  of  the  nutrients  the  coeffi- 
cient is  somewhat  less  than  was  obtained  elsewhere.  This  may  be 
accounted  for  by  the  fact  that  the  hay  used  had  lost  a  considerable 
proportion  of  its  leaves  in  curing,  and  the  Colorado  Plxperiment  Sta- 
tion has  shown  that  these  are  the  most  digestible  portions  of  the 
plant. 

The  dry  matter  eaten  per  day  was  somewhat  less  than  a  mainte- 
nance ration.  The  proteids  were  far  in  excess  of  the  amount  required, 
yet  steer  No.  2  lost,  and  steer  No.  1  gained  only  a  small  amount  of 
this  nutrient,  which  shows  that  the  excess  of  proteids  was  evidently 
used  to  serve  the  function  of  carbohydrates. 

Table  11. — Experiment  No.  .5-- Com  position  of  the  alfalfa  fid.  if  the  nfuse,  and  of  the 

feces. 


[Nutrients  n'i)orted  water  fnv.) 
Water.        Ash.        Protein.        Fat. 


.Mfalfa  as  fed 

.Mfalfa,  water  tree 

Refuse,  water  fn-e.  steer  .N'o.  1 . 
Refuse,  water  free,  steer  No.  2. 


Per  crnl.    /' 
.■■.(19 


rrrrnt.  }'rr  rrnt.  I'trrnU.  I'rr  crnl.  I'rr  cent.  Prr  cnit. 

9..%s  i:i.37  i.9(,  w.CA  :«».:<6  s.-,.33 

l().l)!»  14.09  2.07  .32.28  41.47  89.91 

10.09  14.09  2.07  :f2.28  41.47  S9.91 

10.09  H.mt  2.07  32.28  41.47  89.91 


30 


DIOKSTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE, 


Table  1 1. — Erperhnent  Xo.  5 — Composition  of  the  alfalfa  fed,  nf  the  refuse,  and  of  the 

feces — Con  tinned. 


Feces  o(  steer  No.  1 : 

First  (lay 

Second  day 

Third  day 

Fourth  day 

Fifth  day 

Feces  of  steer  No.  2: 

First  day , 

Second  day 

Third  day 

Fourth  day 

Filth  day 


Water. 

Ash. 

Per  cenl. 

Per  cent. 

78.27 

13.31 

78.09 

11.35 

75.75 

14.11 

78.98 

15.80 

77.24 

10.55 

84.87 

16.15 

88.56 

13.19 

80.97 

15.56 

81.82 

15.41 

74.99 

13.61 

Protein. 


Per  cenl. 
11.50 
10.53 
10.68 
10.67 
11.74 

11.57 
10.72 
10.63 
11.57 
10.63 


Fat. 


Per  cent. 
2.17 
2.11 
2.52 
3.00 
3.16 

2.26 
3.18 
3.37 
3.51 
3.36 


Crude    i^A^If^r"  Organic 
fiber.        'r^„^*       matter. 


Per  cent. 
44.52 
42.73 
45.06 
41.19 
42.02 

43.68 
46.67 
42.56 
43.37 
46.54 


Per  cent.  Per  cent. 


28.50 
33.28 
27.63 
29.34 
32.53 

26.34 
26. 24 
27.88 
26.14 
25.86 


86.69 
88.65 
85.89 
84.20 
89.45 

83.88 
S6.81 
84.44 
84.59 
86.39 


Table  12. 


■Weight  of  the  feed,  refuse,  and  feces  in  experiment  No.  5,  with  the  calculated 
digestion  coefficient. 


STEKRNO.  1. 


Dry 
matter. 


Ash. 


Grams. 

Total  alfalfa  fed 32,274. 1 

Total  refused 121.1 


Total  eaten 32, 153. 0 


Feces:  | 

First  day 2,162.1 

Second  day 2,952. 4 

Third  day 2,934. 3 

Fourthday 2,979.6 

Fifth  day 2, 981. 6 

Total  feces  dropi)ed 14,010.0 

Total  digested 18, 143. 0 

Coefficient  of  digestion   (per 
cent) 


56.43 


Grams. 

3,256.5 

12.2 


Protein. 

Grams. 

4,547.4 

17.1 


Fat. 

Grams. 

668.1 

2.5 


tract. 


fiber. 


Grams.      Grams. 

10,418.1      13,384.0 

39.1     '        29.1 


3,244.3       4,530.3 


665.6     10,479.0 


287.8 
335.1 
414.0 
470.8 
314.6 

1,822.3 
1,422.0 

43.83 


248. 6 
310.9 
313.4 
317.9 
350.0 

1,540.8 
2,989.5 

65.99 


46.9 
62.3 
73.9 
89.4 
94.2 

366.7 
298.9 


%2.6 
1,261.6 
1,322.2 
1,227.3 
1,252.9 

6,026.6 
4, 452. 4 

42.49 


13,384.9 


Organic 
matter. 


Grams. 

29,017.6 

87.8 


28,929.8 


616.2 
982.5 
810.8 
874.2 
969.9 

4,253.6 
9,101.3 


1,874.3 
2,617.3 
2,520.3 
2,508.8 
2,667.0 

12, 187. 7 
16, 742. 1 

57.87 


STEER  NO.  2. 


Total  alfalfa  fed 

32,274.1       3,256.5 
None.        None. 

4,547.4 
None. 

668.1      10,418.1      13,384.0       29,017.6 

Total  refused 

-None.        None.        None.          None. 

Total  eaten 

32,274.1     1  3,256.5 

4,547.4 

668.1      10,418.1      13,384.0       29,017.6 

Feces: 

First  day 

2,258.2           364.7 
1,947.1           25«).8 

261.3 
208.7 

51.0          986.4           594.8         1,893.5 

61.9           908.7          511.0         1, 600.3 

Third  day 

2,816.4           438.2          299.4 
3,245.1     ,          0.1           375.5 
4,150.4    {      564.9           441.2 

94.9       1,198.7           785.2         2,378.2 

F'ourth  day 

113.9       1,407.4  •      848.2         2,74.5.0 

Fifth  day    

139.5       1,931.6       1,073.2         3,585.5 

ToUl  feces  dropped 

Total  digested       .        

14,417.2       2,124.7       1,586.1 
17,8.56.9       1,131.8       2,961.3 

.S5.33           34.75          65.12 

5.5.88           39.29           65.56 

461.2       6,432.8       3,812.4       12,292.5 
206.9       .3.98.";.  3       9,  .571. 6       16,72.5.1 

Coefficient   of   digestion    (per 

30.97          ;K.20           71..';2            57.63 

Average  coefficient  of  digestion 
(per  cent) 

37.94           40.35          69.84            57.75 

AVERAGE   DIGESTIBILITY   OF   RATIONS   USED. 


31 


EFFECT  OF   PRICKLY   PEAR  ON   THE   DIGESTIBILITY   OF   OTHER   FEEDING 

STUFFS. 

From  Table  13  it  may  be  seen  that  in  feeding  a  mixed  ration  of 
prickly  pear  and  alfalfa,  or  prickly  pear  and  cotton-seed  meal,  the 
general  effect  is  to  increase  the  digestibility  of  all  three  feeds.  This 
table  shows  an  increase  in  the  digestible  dry  matter  of  all  three,  and 
with  some  exception  there  is  an  increase  in  the  digestibility  of  the 
nutrients  in  them  all. 

If  the  ration  of  prickly  pear  will  increase  the  digestibility  of  all 
feeding  stuffs,  as  it  apparently  has  that  of  alfalfa  and  cotton-seed 
meal,  then  this  feed  has  a  greater  value  than  is  shown  by  its  own 
digestible  nutrients.  The  probabilities  are  that  the  addition  of  this 
green  and  succulent  feed  to  any  dry  feeding  stuff  will  increase  the 
digestibility  of  both. 

Table  IS.^Average  digestifrility  of  prickly  pear,  alfalfa,  and  cotton-seed  meal,  and  of 
a  mixed  ration  of  alfalfa  and  prickly  pear,  and  cotton-seed  meal  and  prickly  pear. 


Dry 
matter. 


Ash. 


Per  cent.   Per  cent. 


Prickly  pear  alone 

Alfalfa  alone 

Cotton-seed  meal  alone 

Alfalfa  and  prickly  pear 

Cotton-seed  meal  and  prickly 
pear 


64.91 
55.88 
73.70 
68.41 

74.86 


35.69 
39.29 
23.70 
80.59 

57.32 


Protein. 

Fat. 

Per  cent. 

Per  ceiU. 

49.56 

68.46 

65.56 

37.94 

88.40 

93.30 

60.65 

52.28 

73.70 

103.70 

Crude     ^^f^-  Organic 
fiber.     !  'i^„»        matter. 


Per  cent.  Per  cent.   Per  cent. 
72.76 


76.10 
64.38 


47.66 

80.77 

40.35 

69.84 

55.50 

60.60 

37.27 

78.65 

35.55 

68.77 

Table  14. — Summary  of  all  digestion  coefficients  obtained  in  th-ese  experiments,  together 
with  some  coefficients  of  alfalfa  and  cottonseed  meal  as  determined  elsewhere. 


Feed. 


Prickly  Pear  (OpuTitia  lindheimeri)... 
Do 


.\verage. 


Prickly  pear  (O.  Isevit?) . 
Do 


Steer  I    Dry 
No.    matter. 


Per  ct. 

1  !    67. 12 

2  I    64.61 


Ash. 


Per  ct. 
37.46 
33.67 


65.86       35.57 


65.52 
62.40 


38.88 
32.74 


Average 

.\verage8  of  both  above  averages 

Prickly  pear,  calculated  from  feed  of 

prickly  pear  and  alfalfa o  1 

Do 2 

Prickly  pear,  calculated  from  feed  ol 

prickly  pear  and  cotton-seed  meal. . .  1 

Do i  2 


63.96 
64.91 


35.81 
35.60 


"56.81 
60.61 


64.50 
65.29 


-16.87 
44.11 


Pro- 
tein. 


Per  ct. 
59.03 
57.47 


58.25 


39.43 
42.31 

40.87 
49.56 


Fat. 


Per  ct. 
67.42 
68.38 


67.90 


60.18 
68.86 


Nitro-  [ 
Crude      gen-    i  „„„,„ 
fiber,     file  ex-    K*"*«' 

tract. 


Or- 


matter. 


Per  ct.  Per  ct.  j  Per  ct. 

41.31  83.40         71.21 

41.32  81.78  j       77.03 

41.32  82.59  I       74.12 


55.96 
51.02 


60.02 
68.46 


53.99 
47.66 


79.87 
78.03 

78.95 
80.77 


72. 55 
70.12 

71.3!) 
72.76 


-16.54 
40.88 


39.01  j-41.89 
39. 9«   —38.31 


73.97 
80.14 


88.08 
88.11 


29.92 
44.63 


39.03 
39.48 


76.74 

82.88 


81.67 
82.23 


6;?.  09 
75.  49 


72.19 
72.74 


Average ]    64.90  j    39.49  1-40.60       88. 10  |    39.26,    81.95         72.47 

a  The  digeiition  coefTicients  ohtalnwl  from  st«»r  No.  1  that  was  Jed  a  ration  of  prickly  |>e«rand  alfalfa 
are  all  evidently  too  low  and  should  not  be  used  in  the  preparation  ol  rations  from  cither  prickly  i)ear. 
Hlfalfa,  or  the  mixed  feed. 


32 


DIOESTIBILITY    OF    PRICKLY     PEAR    BY    CATTLE. 


T.\BLE  14. — Snmniary  »/  all  diffexlion  roellicifiils  obtained  in  these  experiments,  together 
vilh  some  cofjfinenls  of  alfalfa  ami  cotton-seed  meal  as  determined  elsewhere — Con. 


Feed. 

St«er 
No. 

al 
2 

Dry 
matter. 

Per  ct. 
56.84 
65.87 

Ash. 

Pro- 
tein. 

Fat. 

Crude 
fiber. 

Per  ct. 
35.80 
42.51 

Nitro- 
gen- 
free  ex- 
tract. 

Or- 
ganic 
matter. 

Per  ct. 
21.46 
43.22 

Per  ct. 
40.84 
56.65 

Per  ct. 
51.41 
62.89 

Perct. 
75.09 
80.36 

Per  cl. 
61.57 

Ho 

70.34 

61.36 

67.46 
08.17 

32.34 

48.75 

57.15 

39.16 

77.73 

65.96 

I 
2 

Prickly  })ear  and  cotton-seed  meal. . . . 
Do                               

30.03       74.53 
39.05       72.33 

91.56 
91.41 

44.28 
44.05 

77.97 
77.97 

73.60 
74  15 

67.82 

39.04       73.43 

91.49 

44.17 

77.97 

73.88 

1 
2 

56.43 
55.33 

43.83 

65.99 

44.91 
30.97 

42.49 
38.20 

68.15 
71.. 52 

57  87 

Do 

34.75 

65.12 

57.63 

55.88 

39.29       eS.-'H) 

37.94 

40.35 

69.84 

57.75 

2 

Alfalfa  when  fed  with  priolily  pear 

Do 

39.35 
68.41 

38.90       29.76 
80.50       60.05 

26.54 
52.28 

26.65 
.17. 29 

57.04 
78.65 

42.24 
64.38 

53.88 

50.75  ,     45.21 

39.41  1     31.97 

67.85 

53.31 

Alfalfa,    Colorado    K.xperiment    Sta- 
tion .  .*. 

63. 95 

00.20 
57.00 

57.67       72.54 
40.  itO       77. 00 

29.86  j     49.93 

.54.00       49.00 
48.40       43.30 

72.89 

71.80 
64.00 

-Mfalfa:'' 

Maximum 

Minimum 

38.00 

68.80 

-Xverage 

58.90 

39.50 

72.00 

51.00       46.00 

60.20 

Alfalfa,  Minnesota    Kxperiment  Sta- 
tion   

65.84 

.')9.40 
58.25 
60.03 
60.16 

51.48 

63.49 
56.41 
60.90 
40.85 

75.38 

78.  .52 
75.14 
76.70 
70.30 

.55.88 

57.57 

71.86 

7.5.31 
71.99 
75.24 
71.80 

tlon: 
First  cut 

(50.00 
30.39 
51.65 
50.57 

46.10 
50.44 
50.63 
45.67 

Second  cut 



Third  cut 

Alfalfa,  I'tah  Kxperiment  Station 

Cotton-seed  meal:* 

83.90 
(iS.OO 

38.00 
3.00 

96.10 
83.50 

103.20 
87.30 

100.00 
19.50 

71.00 
43.80 

S7.00 

Minimum 

69.10 

.\  verage 

73.70 

23.70 

88.40 

93.30 

55.50 

60.60 

76.10 

1 
2 

Cotton-.secd  meal  from  feeil  of  cotton- 
seed meal  with  pricklv  pear 

72.84 

76.88 

47.42 
67.22 

77.51 
60.89 

102.7 

37.04 

64.83 
72.71 

7.5.09 

Do 

104.6 

.14.06 

77.28 

Average 

74.86 

57.32 

13.70 

103.  7         35. 55 

68.77 

76.19 

o  The  digestion  coefficients  obtained  from  steer  No.  1  that  was  fed  a  ration  of  prickly  pear  and  alfalfa 
are  all  evidently  too  low  and  should  not  be  used  m  the  preparation  of  rations  from  either  prickly  pear, 
alfalfa,  or  the  mixed  feed. 

b  Bulletin  77,  Office  of  Kxperiment  Stations,  United  States  Department  of  .\griculture. 


SUMMARY    OF    THE    FIVE    DIGESTION    EXPERIMENTS. 


33 


Table  15.-  Daily  rations  fed  during  the  Jive  digestion  periods,  and  a  maintenance  ration 
for  each  steer  calculated  from  Wolff's  feeding  standard  for  oxe7i  at  rest  in  stalls. 

STEER  NO.  1. 


Experi- 
ment 

No. 


Feed. 


Digestible  organic  matter. 


Dry 
matter. 


1 j  Prickly  pear   {Opuntia  lind- 

I      heimeri) 

2 '  Prickly  pear  (O.  Ixiisf) ... 

3 ;  Prickly  pear  and  alfalfa 

4 !  Prickly  pear  and  cotton-.seed 

meal 

5 Alfalfa 

Maintenance  ration 


Pounds. 
13.84 
6.64 
12.99 

14.14 
14.19 
15.10 


Protein. 


I   Carbo- 
Ihydrates. 


Fat. 


Pounds. 
0.  42  ^ 
.11  I 

.35  ' 

1.68  . 
1.31 
.60  I 


Pounds. 

7.44 

'  3.57 

6.48 


Pounds. 
0.13 


Total 
nutri- 
ents. 


Pounds. 
8.00 
3.76 
6.94 

8.43 
7.40 
7.66 


STEER  NO.  2. 


Nutri- 
tive 
ratio. 


1:18.23 
1:33.56 
1:19.13 

1:  4.49 
1:  4.75 
1:12 


Prickly  pear  (Opuntia  lind-  \ 

heimeri) 

Prickly  pear  (O.  Ixiisf) 

Prickly  pear  and  alfalfa 

Prickly  pear  and  cotton-seed 

meal. 

5 1  Alfalfa 

i  Maintenance  ration 


12.98 

0.40 

6.98 

0.13 

7.50 

9.36 

.16 

5.02 

.11 

5.29 

16.44 

.56 

8.93 

.17 

9.66 

17.35 

1.75 

8.09 

.68 

10.52 

14.23 

1.32 

5.98 

.11 

7.40 

16.70 

.67 

7.65 

.14 

8.43 

1 

1:18.23 
1:33.04 
1:16.65 

1:  5.52 
1:  4.74 
1:12 


Table  16. —  Weight  of  feed  eaten,  feces  and  nrine  excreted,  and  water  drunk  during  the  five 

digestion  periods. 


Ex- 
peri- 
ment 

No. 

steer 
No. 

Feed. 

Weight  of  feed  for     Average  weight  of 
Ave  days.         |       feed  per  day. 

Weight  of  feces  for 
five  days. 

'  Grams. 

Pounds.     Grams. 

Pounds. 

Grams. 

Pounds. 

i 

f      1 

Prickly  piear  {Opuntia  lind- 

"i 

heimeri) 

187,53!t 

413.63 

46,884. 75 

103.41 

62,766 

138.43 

I      2 

Prickly  pear(0.  lindtieimeri) 

179,314 

395.48 

44,828.5 

98.87 

58,591 

129.23 

2 

(      1 

Prickly  pear  (0.  l3eri.<i'!) 

121,322 

267.58     2,426.44 

53.52 

20,293 

44.75 

I      2 

Prickly  pear  (0.  laetis) 

'  163, 620 

360.89  '32,726 

72.18 

38,896 

85.79 

Prickly  pear 

95,580 

210.81    19,116 

42.16 

1  1  Alfalfa 

Total 

10,205 

22.51     2,041 

4.50 

3 

105,785 

233.32   21,157 

46.66 

63,355 

139.73 

f  Prickly  pear 

129,627 

285.  m 

25,925. 4 

57.18 

2     Alfalfa 

i 

,1           Total 

'  10,702 

23.60 

2,140.4 

4.72 

140,  ;e9 

.•{09.49   28,0fi5.8 

61.90 

73,485 

162.07 

84  498 

186.36    16,8<»9.8 
23.92     2,169.0 

37.27 

1 

'  10,845 

4.78 

4  ' 

\           Total 

! 
[Prickly  pear 

95,343 

210.28 

19,()6S.8 

42.05 

54,605 

120.43 

106,645 

235.21    21,329.0 

47.04 

1 

2 

11,318 

24.96     2,26a  6 

4.99 

r                

, 

I           Total 

117,963 

260.17   23,592.6 

52.03 

75,155 

165.78 

i  I 

Alfalfa 

339,922.4 

749.72  '67,984.5 

149. 94 

62,800 

138.51 

Alfalfa 

340,080 

750.0    JeS,  010.0 

180.0 

81,190 

179.07 

a  This  experiment  lasted  for  a  period  ol  four  days  only. 


34 


DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 


T.\Bi-E  16. —  Weight  of  feed  eaten,  feces  and  urine,  excreted,  and  water  drunk  during  the  five 
digestion  periods — Continued. 


Ex-  ! 
peri- 
ment 
No.  1 

Steer 

No. 

Food. 

Average  weight  of 
feces  per  day. 

Weight  o 
fivec 

urine  for 
lays. 

Pounds. 

Average  weight  of 
urine  per  day. 

Grams. 

Pounds. 

Grams. 

Grams. 

Pounds. 

ol 

(   ■ 

1      2 

1 

2 
I 

2 

1 

2 

1 
2 

Prickly  pear  (Opuntia  lind- 
heimeri) 

15,691.5 
14,647.75 
4,058.  6 
7,779.2 

34.61 
32.31 
8.95 
17.16 

51,981 
38,915 
26,874 
50,848 

114.65 
85.83 
59.27 

112.15 

12,995.2 
9,728.75 
5,.T74.8 

10,169.6 

28.66 

2 

Prickly  pear  (O.lindheimeri) 

Prickly  pear  (0.  Irvisf) 

Prickly  pear  (0.  Isrt'is) 

Pricklv  pear 

21.46 
11.85 
22.43 

' 

.Vlfalfa 

Total 

12,671 

27.94 

31,700 

69.92     6,340 

13.98 

3 

f  Prickly  pear 

Alfalfa 

Total 

1 

14,697 

32.41 

42,222 

9a  12     8,444.4 

1&62 

1 

1 

' 

• 

,  Cotton-seed  meal 

Total 

10,921 

24.09 

28,975 

63.91     5,795 

12.78 

4 

1 

1 

1 

1 

Total 

1 

15,031 

33.15 

37,525 

82.76     7.505 

16.55 

Alfalfa 

12,560 
16,238 

27.70 
35.81 

44,785 
43,910 

98.77 
96.84 

8,959 

8,782 

19.75 

5  1 

Alfalfa 

19.37 

1 

Ex- 

peri- 

Steer 

ment 

No. 

No. 

ol 

1  I 

2 

1      1 
I      2 

f 

Feed. 


Prickly  pear  (Opuntia  lindheimeri). 

Prickly  p<'ar  (O.  lindheimeri) 

Prickly  pear  (O.  lapvisf) 

Prickly  pear  (O.  latvis) 

Prickly  pear 

Alfalfa 


Weight  of  water 
drunk  for  five  days. 


Average  weight  of 
water  per  day. 


Grams. 


Pounds. 


Grams. 


None. 
None. 
17,225 
12,275 


None. 

None. 
37.99 
27.07 


None. 

None. 
3,445 
2,455 


Pounds. 


None. 

None. 
7.00 
.5.41 


Total. 


41,263 


[Prickly  pear. 
Alfalfa 


I  Total 

i  Prickly  pear 
Cotton-seed  meal. 
Total 


43,240 


66,700 


[Prickly  pear 

2   iCotton-seed  meal. 


91.01 


8,252. 6 


18.2 


95.37 


8,648 


19.07 


147.11         13,340 


29.42 


•Total. 


1  Alfalfa. 

2  Alfalfa. 


83,475 


184.11 


16,695 


36.82 


106,480 
110,980 


234.80  j      21,296      :  46.97 

244.77        22,196  48.95 


a  This  experiment  lasted  for  a  period  of  four  days  only. 


.     GAIN    OK    LOSS    OF    NITROGEN.  35 

INCOME    AND    OUTGO    OF    NITROGEN. 

In  Table  17  is  given  the  income  and  outgo  of  nitrogen  for  both 
steers  during  the  five  digestion  periods.  The  gain  or  loss  of  nitrogen 
is  the  difference  between  the  amount  taken  into  the  animal  as  food 
and  the  sum  of  that  which  is  excreted  in  the  feces  and  urine. 

It  is  interesting  to  note  that  in  the  first  digestion  period,  when  the 
steers  were  fed  prickly  pear  {Opuntia  Undheimeri)  alone  which  had  a 
nutritive  ratio  of  1  to  18.23,  they  each  gained  nearly  1  pound  of  pro- 
teids  in  the  four  days.  Steer  No.  1,  for  example,  ate  1,322.8  grams 
(2.9  pounds)  of  protein  and  gained  453.1  grams  (1  pound)  or  34.26 
per  cent. 

Prickly  pear  alone  was  the  ration  also  for  the  second  period,  but  in 
this  experiment  a  different  species  was  used,  as  well  as  different  steers, 
and  the  latter  were  fat  from  a  previous  grain  ration  and  not  accus- 
tomed to  eating  prickly  pear.  Analysis  shows  that  the  feed  from 
this  species  of  prickly  pear  has  about  1  per  cent  less  protein  than  the 
species  fed  in  the  first  period.  The  steers  ate  only  about  half  the 
ration  eaten  by  the  steers  for  the  first  period  and  digested  about  18 
per  cent  less  of  the  protein.  As  a  consequence  the  nutritive  ratio  in 
this  feed  was  1  to  33  for  both  steers,  and  each  lost  over  one-half  pound 
of  protein,  or  nearly  50  per  cent  of  that  eaten  during  their  five-day 
digestion  period.  Steer  No.  1,  for  example,  consumed  99.2  grams 
and  excreted  146.1  grams  of  nitrogen  in  the  five  days,  making  a  loss 
of  293.1  grams  (0.65  pound)  of  protein,  or  47.28  per  cent.  In  the 
third  digestion  period  steer  No.  1  ate  42.16  pounds  of  prickly  pear  and 
4.5  pounds  of  alfalfa  daily,  while  steer  No.  2  ate  57.18  pounds  and 
4.72  pounds  of  alfalfa.  Something  went  wrong  in  this  experiment 
with  either  steer  No.  1  or  our  analyses,  we  can  not  say  which,  although 
fairly  closely  agreeing  duplicate  determinations  were  secureil  in  all 
the  analyses.  Table  17  shows  a  low  digestion  coefficient  by  this  steer 
for  all  the  nutrients.  This  animal  consumed  312.4  grams  of  nitrogen 
for  the  five  days,  and  excreted  346.5  grams,  making  a  loss  of  213.1 
grams  of  protein,  or  10.9  per  cent  of  the  nitrogen  consumed.  There 
was  excreted  in  the  urine  51.76  per  cent,  while  with  steer  No.  2,  on 
practically  the  same  ration,  only  28.16  per  cent  of  the  nitrogen  was  in 
the  urine. 

The  results  obtained  with  steer  No.  2  were  more  satisfactorv'^ 
throughout.  He  showed  a  normal  digestion  coefficient  for  all  the 
nutrients,  but  it  was  hardly  enough  for  the  proteids  to  make  a  theo- 
retical maintenance  ration  for  him;  yet  we  find  a  daily  gain  in  Table 
17  of  127.6  grams  of  this  nutrient. 

There  was  a  quite  uniform  gain  of  nitrogen  for  both  steers  during 
the  fourth  cUgestion  period  in  which  prickly  pear  and  cotton-seed 
meal  composed  the  ration.  The  gain  for  steer  No.  1  amounted  to 
30.46  per  cent,  and  for  steer  No.  2,  23.07  per  cent. 


36 


DIGESTIBILITY    OP    PRICKLY    PKAR    BY    CATTLE. 


Fifteen  pounds  of  alfalfa  per  day  was  the  ration  for  both  steers 
during;  the  fifth  period.  The  (ho:estion  coefficient  for  the  two  was 
close  enou<i;li  to  make  a  nutritive  ratio  for  both  of  1  to  4.75. 

From  Table  15  it  may  be  seen  that  steer  No,  1  digested  or  retained 
in  his  system  1.31  pounds,  and  No.  2,  1.32  pounds  of  protein  during 
this  period.  According  to  Wolff's  standard  for  oxen  at  rest  in  stalls 
these  figures  are  0.71  pound  for  steer  No.  1  and  0.65  pound  for  steer 
No.  2  in  excess  of  the  amount  required  for  maintenance;  yet  we  find 
that  during  the  five  days  steer  No.  1  gained  only  302.5  grams  (0.66 
pound)  of  protein,  and  steer  No.  2  actually  lost  222.5  grams  (0.5 
pound).  Why  there  should  be  such  a  slight  gain  of  protein  for  steer 
No.  1  and  a  loss  for  No.  2  when  the  proteids  actuall)^  digested  by 
both  were  far  in  excess  of  the  estimated  amount  required  we  are  at 
a  loss  to  say.  It  may  be  explained,  however,  by  the  supposition 
that  because  of  the  narrow  nutritive  ratio  of  the  feed  neither  steer 
had  a  maintenance  ration  of  nonproteids,  and  to  supply  the  necessary 
energj^  their  bodies  broke  down  the  proteids  and  used  the  nonni- 
trogenous  part  of  the  molecule,  excreting  the  nitrogenous  portion 
produced  from  the  cleavage  through  the  kidneys.  That  such  is  the 
case  would  seem  to  be  shown  by  the  fact  that  steer  No.  2,  for  exam- 
ple, in  consuming  727.6  grams  (1.6  pounds)  of  nitrogen  excreted 
509.4  grams  (1.1  pounds)  or  70.01  per  cent  in  the  urine. 

T.ABLK  17. — Income  and  outgo  of  nitrogen  during  the  five  digestion  periods. 


Ex-  I 
peri- 
men  t  ; 

No.  I 


Ex- 
peri, 
ment 

No. 


Feed. 


Steer  Nitrogon  Nitrogen 
No.  ,  in  urine,    in  feces. 


Prickly  l)ear  (Opuntia  lindheimrri) .  ..\\ 

I*riclcl.v  pear.  (O.  laeris?) \ 

Prickly  pear  {0.  engetmimnii  cycloi-  j( 

des)  and  alfalfa 

Prickly  pear  (O.  engelmannii  cycloi 

des)  'and  cotton-seed  meal. . 


.\lfalfa. 


drams.  :  Orams. 


.  52.5 
47.1 
86.0 
121.5 
101.7 
100.9 
.359.  .1 
431.5 
430.0 
500.4 


86.G 

84.4 

60.1 

81.7 

184.8 

1.55.3 

207.7 

242.2 

246.5 

253.8 


Total  ToUl  Nitrogen 
nitrogen  nitrogen  (gain,  + ; 
excreted.  I    eaten,      loss,  — ). 


Grams. 
139.1 
131.5 
146.1 
2m.  2 
.346.5 
256.2 
.167. 0 
67.3.7 
676. 5 
763.2 


Orams. 
211.6 
198.4 
99.2 
140.0 
312. 4 
.358.3 
815. 3 
875. 7 
724.9 
727.6 


Orams. 
+  72.5 
+  66.9 

-  46.9 

-  63.2 

-  .34.1 
+  102.1 
+248.3 
+202.0 
+  48.4 

-  35.6 


Feed. 


Steer 

i  No. 


Prickly  pear  (Opuntia  Undhfimeri) \l  i 

Prickly  pear  (O.  tetn*  ?) !|  ^ 

Prickly  pear  (O.  engelmannii  cycloides)  \j  1 

and  alfalfa 1  2 

Prickly  pear  (O.  engelmannii  cycloides)  \(  1 

and  cotton-seed  meaL 'l  2 

Alfalfa 'I  I 


Protefiife 

(gain,  +; 
loss,  — ). 


Grams. 
+     453.1 
+     4iai 

-  293.1 

-  .395.0 

-  213.1 
+  638.1 
+  1,551.9 
+  1.262.5 
+    302.5 

-  222.5 


Nitrogen 

(gain,  + ; 
loss,  — ) . 


Per  cent. 
+34.26 
+33. 72 
-47.28 
-45.14 
-10.92 
+28.50 
+30.46 
+23.07 
+  ft.  68 
-  4.89 


Excreted  I  Excreted 
nitrogen  (  nitrogen 
In  feces,    i    in  urine. 


Per  cent. 
40.93 
«2.54 
60.58 
58.35 
59.15 
43.34 
25.47 

si'oo 

34.88 


Per  cent. 
24.82 
23.74 
86.69 
86.79 
51.76 
28.16 
54.09 
49.16 
59.32 
70.01 


SUMMARY    OF    RESULTS.  37 


CONCLUSIONS. 


(1)  The  average  digestibility  of  the  nutrients  of  prickly  pear  as 
determined  in  the  first  experiment  where  Opuntia  lindheimeri  was 
used  were:  Dry  matter,  65.86  per  cent;  ash,  33.68  per  cent;  pro- 
tein, 57.47  per  cent;  fat,  68.38  per  cent;  crude  fiber,  41.32  per  cent; 
nitrogen-free  extract,  81.78  per  ccnt^ 

In  the  second  experiment  where  the  variety  0.  l^visf  was  used 
the  coefficients  of  digestion  were:  Dry  matter,  63.96  per  cent;  ash, 
35.81  per  cent;  protein,  40.87  per  cent;  fat,  69.02  per  cent;  crude 
fiber,  53.99  per  cent;  nitrogen-free  extract,  78.95  per  cent. 

In  general  these  results  would  perhaps  show  a  somewhat  low 
coefficient  for  protein,  a  decidedly  low  coefficient  for  ash,  but  a 
very  liigh  coefficient  for  the  nitrogen-free  extract.  The  total  digest- 
ible nutrients  are  about  equal  to  those  of  immature  green  corn  fodder. 

(2)  Our  experiments  seem  to  show  that  when  prickly  pear  is  fed 
with  cured  fodders  or  grains  the  digestibility  of  both  is  increased. 
For  this  reason  prickly  pear  has  a  greater  food  value  than  is  shown 
by  its  analysis  and  digestion  coefficients. 

(3)  The  nutritive  ratio,  i.  e.,  the  ratio  of  })roteids  to  carbohy- 
drates, is  very  wide  for  this  feed,  and  in  feeding  it  to  all  classes  of 
animals,  fpr  whatever  purpose,  much  better  results  should  be  obtained 
when  it  is  fed  with  some  substance  of  a  high  protein  content. 

(4)  While  the  digestibility  of  the  ash  was  apparently  small,  as 
noted  above,  yet  the  large  amount  of  ash  contained  in  these  plants 
caused  more  ash  to  be  assimilated  from  a  ration  e(|uivalent  to  15 
pounds  of  dry  matter  than  is  ordinarily  assimilated  from  an  ecjual 
ration  of  alfalfa,  which  has  a  higher  coefficient  of  digestion  for  its  ash. 

(5)  The  steers  seldom  drank  water  when  fed  prickly  pear  alone. 
In  fact,  in  feetling  a  ration  of  100  pounds  of  this  feed  per  day  the 
animals  obtained  from  the  feed  over  S  gallons  of  water,  which  is 
more  than  was  usually  drunk  by  them  when  fed  curetl  fotlders  alone. 

(6)  While  no  digestion  experiments  wore  made  with  any  of  the 
cacti  other  than  prickly  pear,  the  digestion  coefficients  of  the  latter 
could  probably  be  safely  used  for  all  other  members  of  this  family, 
since  their  composition  and  other  characteristics  are  similar. 

(7)  It  may  be  seen  that  botli  steers  gained  proteids  during  the 
first  experiment,  although  both  ate  a  smaller  ((uantity  of  dry  matter 
which  contained  less  proteids  than  are  re(|uired  according  to  Wolff's 
standard  ration  for  oxen  of  their  weight  at  rest  in  stalls. 

In  the  second  experiment  botli  animals  lost  proteids,  but  here 
steer  No,  1  ate  less  than  half  of  what  was  eaten  by  steer  No.  1  in 
the  first  experiment,  and  steer  No.  2  ate  over  3  j)()un(ls  less  than 
steer  No.  2  of  experiment  No.  1. 


38  DIGESTIBILITY    OF    PRICKLY    PEAR    BY    CATTLE. 

(8)  Animals  scour  (juite  badly  when  fed  prickly  pear  alone;  besides, 
other  feeds  are  needed  to  supply  the  proper  amount  of  proteids; 
and  for  these  reasons  it  is  better  not  to  feed  it  alone. 

A  ration  for  a  l,00()-pound  milch  cow  of  50  pounds  of  prickly 
pear,  10  pounds  of  wheat  bran,  and  10  pounds  of  alfalfa  would 
furnish  about  the  correct  theoretical  amount  of  nutrients,  in  which 
the  ratio  of  proteids  to  carbohydrates  would  be  1  to  5.46. 


O 


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